On Apple iOS and Google Android there are free downloadable apps that allow you to earn small amounts of money using your mobile devices. Find the apps on your own smartphone or tablet via your app store. The benefit of earning extra income using your mobile is you can do it while away from home, such as while commuting on a train.
SlideJoy app test: How much money was made in a 21-day period
Slidejoy was a popular way to earn free money from your smartphone. It closed down in April 2020.