I went to an all you can eat buffet in Berlin to eat something. I entered the restaurant got some food on the plate and sat at the table. The waiter ask me a few question and then tells me that it is obligatory to order a drink which you have to pay extra,( they also had a written sign on the table that specified that.. Can they make that rule that you have to other a drink? And what could I have done? I had already taken a plate, is it legal to do that?