Completely delete an app and the app's cache from iPad I've got an app on my iPad Mini that has a weird bug; the app in question is Trello and whenever I try to write a new card it changes the columns to display sideways and half off the screen. 

I've tried to get around this by just deleting the app and re-installing it from the app store, but when I do that it has the same bug (I've tried the app on other iPad minis and it works fine) so I'm guessing some of the settings / content of the app are cached on the iPad - is that correct? 

If so is there a way to delete an app and its cached content / data at the same time?
App settings aren't cached between installations. Either there's a bug in your app's settings, which it pulls from their API's through their website, or perhaps they have iCloud settings stored.

In the first case you should contact Trello about it or try removing and then re-adding the buggy content through the web version. If the latter is the case, go to Settings, iCloud, Storage, Manage Storage and find Trello. Then press Edit and Delete All.