Savvy savers are raving about the trick, with some saying they don’t need dehumudifiers, which are a popular way to tackle the problem but cost money to run.
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But the gadgets can set you back a couple of hundred pounds for the best models – while the 69p item costs nothing at all to run.
Shoppers can pick up washing up liquid for just pennies in any major supermarket, and probably already have one under the kitchen sink.
The household essential has been branded ‘incredible’ for stopping the winter blight.
One energy saver fed up with damp said: “Lots and lots of condensation every morning and night and day since we moved in and then I saw a video hack and it works.”
“Fairy liquid (or any cheap variant) on a dry cloth, wipe the window so it is covered in the stuff.
“It will look smeared which is fine.”
“Then leave. Don’t dry off. Let it dry naturally.”
They said their window was totally clear the next day, compared to a “mass of water droplets” the previous night.
Condensation forms when moist warm air hits a cold surface, such as external walls and windows.
While windows can be wiped clean, the job can be time consuming especially in larger homes.
The excess moisture if not tackled can then lead to damp and mould, which thrives in these conditions.
We spoke to 33-year-old mum-of-one Francesca Henry, who runs the website and Instagram page The Money Fox, who uses the washing up liquid trick herself.
She suggests using a “very small amount” of Fairy liquid. “This will prevent [the windows] from getting wet,” she said.
You can pick up Fairy for as little as £1 for a 320ml bottle right now at major supermarkets like Asda and Tesco.
But you don’t need to use branded versions and supermarket own-versions can cost just pennies, like Tesco’s original washing up liquid which comes in a bigger 500ml for just 69p.
Prices can vary from one day to the next,so it’s always worth checking that you’re getting the best price.
You can use websites like Trolley.co.uk and Google shopping.
The Latest Deals app has a supermarket comparison tool so you can check prices on the go.
More ways to tackle winter condensation and mould
It’s not the only ways savers are tackling the issue of condensation are also free or very cheap
Some suggest that opening a window at night will help as the ventilation can stop water droplets forming on windows.
As well as ventilation, having the heating on is a way to stop damp and mould forming.
Though many of us are looking to keep it off to keep energy bills down, the temperature you need to put it at is between 18 and 21 degrees, experts say.
There are certain types of plant that can help, like a peace lily which you can pick up for as little as £5.50.
Spathiphyllum as it’s officially known absorbs excess moisture in the air.
Window vacs are pricier but can be used year after year to remove moisture.
One bargain version we tried was better than the popular Karcher brand and cheaper.
Avoiding drying clothes on radiators, putting lids on pots when cooking and using an extractor fan are also recommended.
Meanwhile The Sun reporter Harriet Cooke tried other tricks like salt, baking soda and even cat litter to see if the popular tricks work – read on to see how she got on.