We've shared many ways to speed up, clean up, and revive your iOS device before, but if you're jailbroken, a free app called iCleaner can actually perform a bunch of maintenance tasks with one tap.
We don't think of iOS as holding a lot of "junk" files like we would Windows or Android, but it has caches and temporary folders just like any other operating system. Running iCleaner will let you remove:
- Safari's cache, cookies and history
- Application WebClip caches, cookies, temporary files, and snapshots. It also does a more in-depth cleanup for certain popular apps like Facebook, iFile, Instagram, Twitter, and others.
- Log files and crash reports
- System cache files and databases
- System temporary files
- Partially downloaded Cydia packages and repo files
When you start it up, it will ask you which of these you want to remove, so if you rather like your Safari cookies, you don't have to delete them. Casual users may not find that it frees up a lot of space, but the general consensus seems to be that it'll free up a few hundred megabytes — and some heavier users are noticing a few gigs, even. Regardless, it's a good way to keep your device clean and free up space for a few more songs, if you need it.
iCleaner is a free download for jailbroken iOS devices, available in the default Cydia repositories.