If you always find yourself struggling for cash, the chances are you're spending money on things you don't really need. Save yourself some money by cutting out these 25 unnecessary purchases.

There have been several recent high-profile campaigns against single-use plastic, but still 7.7 billion water bottles are consumed in the UK every year. Sales in £2.4 billion-a-year industry actually increased by 8% in 2017. But given that tap water is a much cheaper alternative, and in Britain among the most highly regulated in the world, avoid buying bottled water to save your wallet, and the planet.

The key to free banking is being honest with yourself about how you use your account, and then track down one offering what you need for free. With banks providing everything from small overdrafts to overseas spending as freebies, there’s no need to pay fees as long as you choose carefully.

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There are people who love to line their walls with books. For everyone else, once you have bought one, you should be able to swap your way through an entire library of books without ever spending another penny. There are plenty of book swapping sites online. If you don't fancy that it’s straightforward to set up your own at work, and you’ll have a never-ending supply of second-hand books at no cost at all.

Statistically, the most likely outcome of playing the lottery in any one week simply involves losing £2. But if you are keen on a flutter, you can actually have do it for free, using freepostcodelottery.com. You just register your postcode, and check back every day to see whether you are that day’s winner. The jackpot is £250, paid for by advertisers, so you never have to hand over a penny.

Wasted food costs the average household £470 a year – and families with children £700 a year. There are three ways to avoid waste. First is planning: make a list of meals for the week before you go shopping. Second is realism: don’t pile the trolley with salad unless your family will eat it. Finally there’s vigilance: halfway through the week, revisit your fridge. If you’ve failed to eat what you thought, this is the time to start freezing.

It’s always a good idea to keep an eye on your credit report – especially if you have ever been a victim of fraud. Most of the credit report companies let you sign up and pay for regular reports. However, many of them also offer a free one-month trial, and some offer free reports anyway, so it’s worth thinking hard whether you need to spend your money on this.

A pedigree pet may be pretty, but it’s pricey. Before you reach for your wallet, therefore, it’s worth considering a rescue pet. The RSPCA rescued over 114,000 pets in 2017, so there’s bound to be one that suits you in a rescue home somewhere around the UK. Rescue animals may require some work to get them back on track, and you will need to find the animal to suit your home and your family, but you can get a much-loved family member for the price of a small donation.

In an environment of rock-bottom rates and lengthy interest-free periods, there’s no reason for anyone to pay interest on their credit card. There may not even be the need to pay a fee to transfer your balance to an interest-free card. The only proviso is that this isn’t an excuse to run up more debt, it should be an opportunity to pay more of it back.

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There’s a minority of people who genuinely forget something vital for their holiday, and have to pick it up at the airport. However, the vast majority of people in airport stores are killing time. A survey by Mintel three years ago revealed that a third of people end up buying something on a whim as a result, so if you think you’ll be bored at the airport, it might be cheaper to take a book (you could even take one from a book swap).

Buying an extended warranty for an electrical item often makes very little sense. Replacing these items is cheaper than it used to be, electrical items are more reliable, and in some cases technology is developing so fast that the item is obsolete before it breaks down. Instead of a warranty, it’s worth checking guarantees from retailers, which may give you two years of cover or more for free anyway.

Nowadays you can get cheap apps for smartphones that do a great job of directing you around unfamiliar areas, so you don’t necessarily need to invest in a sat nav.

It may feel like you are getting better quality when you opt for a brand name, but instead you are paying for a combination of the research the company originally put into developing the drug, and the marketing and advertising it did to build up the brand. If you buy the identical generic drug, you’ll get exactly the same product for a fraction of the price.

We all know service stations can be overpriced, and yet occasionally we all stop off when our travel plans go awry. If you pack emergency rations in the car, there’s never any reason to move beyond the free car park. And if you don’t have anything sensible to take with you, you can always come off the motorway, drive for five minutes, and find a cheaper alternative.

Introductory deals, persuasive salespeople, and tempting bundles can leave us with TV channels we pay for but hardly ever watch. It’s worth asking yourself once or twice a year whether you are getting value for money. If you only watch movies or sport a couple of times a month, it may be far more effective to buy a daily pass, or pay to download a single movie, rather than pay for a package.

The financial model for most of the biggest app games over the last few years is to give away a free version and offer people the chance to make in-app purchases in order to speed up their progress or improve their experience of the game. It’s very tempting, and once you start it’s difficult to stop, but it’s entirely unnecessary. Block in-app purchases and save yourself a fortune.

Keeping your eyes peeled for coupons on your regular purchases is a great idea, and using vouchers to get groceries for free is a no-brainer. However, buying something you don’t need just because you found a coupon offering a discount is no way to save money. Before you print off a voucher, therefore, it’s always worth asking yourself whether this is actually going to save you money.

Before you buy new clothes, you should be asking yourself three questions in order to avoid paying full price. Are there any vouchers for this shop online? Can I get cashback by using a cashback site or a credit card? Can I wait for the sale? You could save at least 5% this way – and if you have the patience to wait for the sale, you could save 70% or more.

There are plenty of traditionalists who love newsprint, but if you want to save money, you can get most of your news and features for free online. If your favourite paper operates a paywall online, you may need to be flexible about where you get your news, but it may just offer the chance to find something that suits you better.

Coffee aficionados aside, there are millions of pounds spent every year on caffeinated drinks and sugary treats used purely to give tired people a boost. There are some people who simply don’t have the time to spare for a good night’s sleep, but if you can put aside eight hours a night, you can save your cash and your health at the same time. If you can't go without? Avoid expensive coffee shops and wait to have a coffee at home or work.

A study by RIFT Tax Refunds found that women are still paying as much as 35% more for razors, deodorant and moisturiser that are marketed at their gender. Dubbed the "pink tax", some stores such as Tesco have attempted to scrap the price difference. So, head to a shop that has changed their prices, or trade your products for a men’s version, and shave a fortune off your razor costs.

There may be a host of incredibly pushy firms offering to reclaim your PPI in return for a fee, but you really don’t need to spend money on this. You can do it yourself, for nothing, using a letter template downloaded from the internet. It will take less than 15 minutes of your time and could save you hundreds of pounds.

You may not realise you are paying for this, because often companies will build their fee into the monthly sums you end up paying. However, in many cases, the costs involved in using a debt company are eye-watering. A far better bet is to use a debt charity like StepChange, who will often offer a far broader range of solutions, without charging you a penny.

Read: where to get free debt advice

While the UK is still part of the EU, it’s worth having one of these cards, which demonstrate that you are entitled to the same free care in EU hospitals as the locals. If you get a form from the Post Office and send it off, you’ll get this card for free. Similarly, you can access a form online and pay nothing for your card. The ‘services’ you need to steer clear of are the online firms that will charge you a fee to apply for your card – they’re most likely scammers.

Pre-sliced food is tempting but in reality is only likely to save a couple of seconds of preparation time – and cost you a packet. Is it really too much trouble to grate cheese or slice carrots?

If you’re blowing your cash on fitness fads, diet supplements, gadgets gathering dust in the cupboard and unused gym memberships, then you need to stop. In most cases, moving marginally more and eating marginally less (or less unhealthily) will do the trick – and that doesn’t have to cost anything.