We use those red plastic throwaway cups from Sam"s Club frequently. But my cat thinks they are her personal drinking bowls. So I made a lid to put on the cups. Problem solved, cat is ticked.

<<<>>> UPDATE: I added a hole for a straw, and I have a printing suggestion. You can significantly improve the thermal characteristics of this lid by carefully controlling how it is printed. I set the layer dimension at 0.16 and the infill at ~15% This reduced infill percentage changes the largest surface area of the lid to have a much lower thermal conductivity. Consequently, your drink will stay cooler or hotter longer.

I've included the STL file for the lid with a hole, and also added a Simplify3D factory file example that prints the first 2mm of the lid at 0.16mm layers, and the remaining (lip) areas at 0.3mm layers. This slightly reduces the print time.