Too-long file name: which iOS app owns it?
The GUID (globally unique identifier) you see is randomly generated by iOS at the time of installation or update, and not related to the app in any way - in fact, it even changes between updates and reinstalls. Previously, apps were kept at /var/mobile/Applications/&lt;GUID&gt;/blah.app with Documents, Library and tmp alongside it in its sandbox, however now in iOS 8 that's changed so /var/mobile/Containers/Bundle/Application/&lt;GUID&gt;/blah.app contains the app and /var/mobile/Containers/Data/Application/&lt;some other GUID&gt; contains the data. Unfortunately, the data and bundle GUIDs don't match, so that's made it a lot harder to track down.

On a jailbroken device, you could use the iFile app from Cydia to navigate through the file system to the offending file and delete it. I would recommend you also check the Library/Preferences folder so you can see the bundle identifier of the app, which should help you determine the offending app, so you can report this issue to the developer. It's worth noting that the developer is using the Documents folder to store caches, which is meant for, well, documents. They should be using Library/Caches, which isn't backed up by iTunes.

You could alternatively use iCleaner Pro (I haven't used it before so I can't give you specific instructions).

Another method if you don't have a/don't want to jailbreak would be to download iFunBox (note for Windows users: download the classic version) and look through the application list manually until you happen to find Documents/iCache/.... Right click the offending file and choose Delete.

A last-ditch method is to fill up your disk with data, which triggers iOS to start clearing app caches to make some room.