How to clear Files app cache on iPad/iPhone

Since last update to iOS12 many users notice and increase of the system size or the iCloude Drive storage on the device. I’m one of them. As you can see I have 17.34GB now filled with something that I don’t know. When you tap on it as you can see on the second attached image apparently your most view files on iCloude Drive. Fine. Tried different questions on the communities, some twitts but apparently there isn’t an answer.

This morning I was thinking a different route. Is anyone aware how to clear the cache of Files app? This will free the space and also will help me and other user to understand how this happen.

Thank you in advance

M

I use iPad Pro 12inch second gen and iPhone 8 Plus