The problem they had was that they had managed to lose the source code of the app, lol. Since the app was a simple webview wrapper I decompiled the apk to some horrendous java monstrocity and carefully extracted all used logic, the html, css and js and created a new webview app with the slightly modified code.
Oh and I had no experience in Java or Android development :)
Another hack I was very proud of:
Some weeks ago I had to pick something up with a car trailer. I went to my parent's place to get it and when checking if the lights worked (it was dark already) it turned out that they did not. Since I was driving to a larger city I could not just go without lights.
The problem was, that I really had to pick this up and also I had no extra time to find an alternative solution, so I wiggled the jack of the trailer's cable in all directions hoping to clear out some oxidation. After some minutes of trying I found a specific position in which the lights seemed to work.
Taking out the good old duct tape from my car's trunk I fixated the jack against the trailer hitch. For some reason it actually worked and did not break. I was very proud of this hack!
Obviously I didn't fix it yet :-P