I know a machine which rocks. The drinks machine in the school canteen! We have a cashless card system, but sometimes the little computer which you put your card into on the front of the machine crashes and so you can just press the buttons on the front of the machine as many times as you can and clean it of as many drinks as you can before it resets. If you're really quick, you can get about 8 out. But shhh, don't tell the canteen staff (or anyone else for that matter, it's my own little trick).