Q: How to delete documents and data of an app iPhone 4s iOS 5.1.1 version

Whqt data app are you using?

You have to delete the app and reinstall it.  Can't just delete the data unless the app itself has a setting to do so (very few do).

Thank u so much tried your advice and deleted some recently installed apps hope this will solve the problem  

Absolutely stupid that I have to delete Facebook and twitter, then reinstall them just to clear cached data I don't even need,

why is the operating system not automatically doing this for me?

Why is this data not stored in my 5gb of iCloud, of which 4.9gb is free?

Why is there not a button to clear docs n data from settings?

All great questions that should be addressed with the app developer.  Some apps do allow the user to clear data but not all do.

For downloaded apps, it sounds like there is a clumsy but workable option to delete and reinstall the app.  But for apps that come with the operating system, is the only alternative to reinstall the operating system?

There is a a thread at https://discussions.apple.com/message/23028563 discussing this issue in the context of the release of iOS7.

But for apps that come with the operating system, is the only alternative to reinstall the operating system?

What specific app?  Some have methods within the app or app settings

Aslo, a restore isn't necessary for anything:

Settings > General > Reset > Erase All Content and Settings

The biggest collection of lost files for me is associated with Mail, and I don't see any way to rease content other than deleting messages.  BTW, it was quite a bother to erase Sent messages since I didn't see a way to delete them all as one can do for Trash. 

"Erase all Content and Settings" does sound somewhat easier than a full reinstall, though it sounds like all preferences and email accounts would have to be set up again.  It seems like there should be a simpler way to delete a program's data.  Normall I would try "Erase all Content and Settings", but it looks like we are all getting new phones so I'm more interested in finding out whether this sloppy file handling is present in both iOS and Android, because if Android is significantly better I might switch so as not to have to erase all my settings from time to time to keep the phone from getting overloaded.  I'd even consider Windows Phone if that was the best solution to this problem.

I would not be surprised if the Mail problem is related to the stuck download progress bug described at https://discussions.apple.com/thread/2528738?start=0&tstart=0, which has been around for at least 3 years, and wasn't even fixed when Steve Jobs was alive so I'm not optimistic that it will get fixed now.

How do I even tell which apps are storing all the data?

For the Facebook App Follow these steps

Click on More at the bottom menu

Scroll down and choos Settings, and Account Settings

Click on Browser

And Click on Clear Data