In iOS 8.3, Apple revoked the user's ability to access a downloaded app's files (Documents & Data). Further, third party apps don’t natively provide a way to delete their "Documents & Data". It's an inconvenient feature in the OS, yet it exists, even from the beta stages.
However, in an attempt to defend Apple, this could have been an extra security measure to prevent users from hacking apps. Another possibility is that the cleaning apps you mentioned are simply not up-to-date with the new OS.
Sadly, you will have to delete the app off of your iDevice, and reinstall it, to remove any app data. You can do this either from the iDevice itself, or using iTunes on a computer.
You could jailbreak your iDevice which would give you access to multiple cleaning tools, but a jailbreak could be difficult to keep up with. You also don't want to accidentally mess with something serious.
It's a sad but certain truth that apps must be removed and reinstalled. Good luck!