The Unfillable Cup looks unassuming… until you try to fill it up. This is my take on a siphoning cup with a focus on being as discreet and hidden as possible while also featuring a fast empty rate. There is no obvious central siphon nor small hole inside the cup. 

Fill it up too far? It will start draining out the bottom.

Fill it modestly? It will wait until you tip it to drink and then it starts draining out the bottom. Even if you tilt it back to vertical, it continues to drain.

Also known as a Pythagorean Cup, a Greedy Cup, a Cup of Justice, or a Devious Cup, the Unfillable cup features a maximum number and volume of hidden siphons. This allows relatively high flow in any orientation. Please Prank Responsibly.

Note on AI: I designed, printed, tested, and iterated this design myself. Some AI was used for beautifying display photos - I have included the original photos as well.