I use cm security and have been using it for some time and it works really well. Funny though, I was just searching for it to post a link and I can't find it. Now I read something about it being pulled. It works really well though.
http://www.igeeksblog.com/how-to-boost-iphone-memory-and-performance-by-clearing-app-cache-and-data/
Too bad, I tried going there from the link on the page above and the item is not available. I've been using it since I've had this phone and it works really well. I use it regularly and can get between 100-200 mb. The only problem I ever had was one weather app it cleared my preferences, but that was the only app it ever affected in a bad way.
Phoneclean is a computer based program you can clean cache, but I got a prompt to upgrade yesterday so I did and now it's a pay program. It works well cleaning app cache though. If you can still find the free version it beats having to uninstall and re install apps.