There are some different apps that you can download and install on your mobile device. They have apps for trivia games that you can play online against other players to earn money. You can enter into a fantasy football game and earn money with your fantasy team or placing bets on other teams.
Many GPT sites have a gaming section on their website. You'll go there and play games to earn money. You won't earn a great deal of money like this, but you can earn some money.
You also have online gaming sites you can join for gambling, bingo, and video challenges against other online players that earn you money.
This will all depend on what you want to do and what games you're interested in playing. Check the app store on your mobile device and you can find plenty of apps that pay you to play games or even download and install games on your mobile device.