The Tantalus cup works normally if it is partially filled. If filled to the brim most of the liquid siphons out through the bottom. It is also called a Pythagorean cup.

Thing:17330 by Scooter46290 is a such a cup with a simple but elegant siphon composed of three concentric cones about a central tube. Here is another version where the siphon is concealed in the stem. It has the advantage that the siphon has a greater head and can more completely empty the cup. Open scad and stl files are provided.