Apps are automatically backed up to your Google account. However, this is dependent on the developer, so you might not be able to find all the apps backed up to your Google account. There are some apps that can even backup app data on the cloud, saving you the trouble of starting fresh when you sign in from a new device. You can find this by navigating to Settings – Backup & Reset – App Data to check if an app is backing up data to the cloud on its own. For apps that don’t however, there’s nothing you can do barring downloading them again and starting fresh. Google still has some work to do on this front, though.