This provides a customizable drinking coaster that can be Lego® compatible. If Lego® compatibility is what you're after, you may need to tweak the nubbin_diam parameter under advanced.

Be advised that 3D prints aren't necessarily water-tight, even if they look as they might be.

STL files for 60, 80, and 100mm diameters are provided for your convenience.

I hope you will find the design useful!