Kwiff is a sports betting app that allows you to bet on a wide variety of sports and has a unique chance of increasing the odds on your bet randomly.
They currently have a promo for referring friends where if you sign up, deposit £5 and then place 1 bet (any value), you also get a free £10 bet from them.
The bet you place can be any value so just place a bet on anything and only put 10p (£0.10) on it to lower the risk of losing money. You will then be credited with the free £10 bet and hopefully it will win.
Make sure to withdraw your remaining £4.90 so that you don't get tempted to spend it all. There is a chance that you lose 10p here but you can win a lot more (some people on Reddit have won over £100)
My referral link to sign up is https://dkn33.app.goo.gl/hPPr (As it is a mobile app it's best to open this on your phone).
Non-referral link is https://corporate.kwiff.com/
* Update: I've won £20 *
Direct Links to Paid Online Work