deleting temp files that are part of installed apps

Hi guys, Offen to make more space, I remove apps dew to the size and then re-install them to get rid of the files and space that the app takes up over time.
Is there an easier way just to get rid of those files.
A good example is facebook.
The app size is lets say 100 mb, but over time the documents and data is an extra 2 or 300 mb, That obviusly takes up space.
How can I get rid of the documetns and data without un-installing the hole app?