Google Opinion Rewards
Google Opinion Rewards is easily one of the best free Android apps in the Google Play Store. To use this app, you simply download and install it, then open it one time. After that, the app will periodically notify you to ask you some questions.
You’ll get credit for use in the Google Play Store every time you answer a survey. That credit can go toward buying yourself apps or games in Google Play. It’s a great way to expand your collection without spending real money. At worst, everyone should have this app installed.