Completely remove an application and its data on iOS 8

I have an application that is not working properly (I always get an error). I know other people who have the same app and for them no errors appears.

I thought that maybe there are temporary data stored and getting rid of them would solve the problem.

As suggested in this answer I tried to remove the app. I tried to delete it in two ways: * By holding my finger on the icon and pressing the x. * And from the menu Settings -> General -> Storage -> Manage Storage.

None of them fixed the problem and I believe that some app data are not removed. I think so because when I remove the app and reinstall it, as soon as I open it I'm already logged in.

Is there a different way of getting rid of app data?