This is a prank cup also known as the greedy Pythagorean cup. This cup was invented by Pythagoras of Samos to make his greedy comrades pay. All you need to understand this cup is a little understanding of the science of syphons. The Pythagorean cup (most commonly) uses a staff in the middle with 2 connected tubes going up and down the inside. As you slowly fill the cup, the water in one of the tubes grows higher and higher until it reaches the top, and all the water is syphoned out the bottom. But my design uses a different, more discreet method where the water is syphoned out the bottom of the handle. There is also no hole besides the "fastener" at the handle. One of my favorite features about my cup though, is that it leaves .5" of water left for the greedy drinkers, so while everyone else has nice sized drink, while Mr. Greedy has a measly mouse's helping.
*Note
Remember to use snug supports if using Bambu Slicer.
This cup is not for hot liquids above PLA's melting point.
Have fun