How do I delete an app's data?

[Nermal]

One of my apps has starting misbehaving recently for no obvious reason, so I suspect that one of its data/settings files has become damaged. How can I delete the app data so that it's back to a clean slate?

If I hold on the app and press X then the message states that both the app and its data will be deleted. However, when I sync the app back onto the phone, the data (account name etc) is still there.

I've turned off "Documents & Data" in iCloud so it's not coming from there. I suspect that iTunes is being "helpful" and copying the data across from my latest backup but I can't figure out how to prevent this.

What should I do?

 

[Intell]

If you delete it from your phone via the X, that'll remove all of its data.

 

[Nermal]

As stated in my first post, the data is still there (back again?) after reinstalling the app.

 

[Nermal]

Update: This is now moot; the app developer released an update since yesterday and it fixes the issue that I was having.

It would still be good to know how to do this in the future though.

 

[Nyy8]

I could be wrong, but don't you delete it. Then reinstall it from the App store? Not from iTunes.