Cup holder that clips onto a table top. By default, the model fits a 20 mm (or a bit thinner) table top and a 70 mm diameter cup.
Print both the top and bottom. You need an M3 bolt roughly 22 mm long and a torsion spring (~3 mm inner diameter, 5 mm wide and with ~20-25 mm long arms). These parameters can be changed in the OpenSCAD code.