After reading this thread, I deleted my weather app and Dropbox, then reinstalled them. Got almost 1 GB of space back. Google + also has to be deleted often, if you use it a lot.
You should only have to log out and log in on the Dropbox and Google apps for their caches to clear.
There should certainly be options to clear cache in an app, for every app. Either on an iOS level or in-app.