The two men had used a milk crate with a false bottom to raid the prison shop. When approaching the cashier they put what looked like a normal crate of milk cartons on the desk.
But the pair had cut the bottom out so they could load in goodies for free.
During a cell-check, guards found the box and turned it over to find not milk inside, but four packets of coffee worth nearly €22.
Inmates at the prison have a €70 monthly limit on what they can buy from their prison shop, which generally stock items such as cigarettes, toiletries and food.
Stephan H. was serving a 12-year sentence for a number of bank robberies and theft of over €600,000. André was given a five-year stay behind bars for assault, according to Bild.