The Pythagorean Cup is a classic practical joke invented by Pythagoras himself, in which a patron who fills his glass too full (traditionally with wine), will have all of his drink drained from his glass (and onto his clothes).
In this design, the volume of the glass holds one drink of wine (5 oz) before draining, allowing one to keep track of their consumption. In addition, it is designed to be easily printed and assembled, as it does not require interior support and has been toleranced for most commercial FDM printers.
Simply print the two provided STL files, and drop the small piece into the slot on the inside of the glass. Superglue can be used to adhere the two pieces, or the print can be used without any fixed assembly.