This was a simple easy print at 15% infill without resizing. You could print multiple in different sizes to fit different cups or do what I did and just print the one to fit whichever cup you're using. Plus you can flip it over for a coaster! Inside? Coaster. Sitting on the porch? Cup cover.
I printed the cover (Left) out of PLA and it fit internally nice, but the outside is too small for my application. I remixed it to be slightly bigger on the outside. (Right)