My friend set up this awesome 10 seat 170" UHD theater in his basement, and he even built a wooden lift for one of his two couches so the room could have stadium seating. Each seat has a cup holder, but he was running into issues where some cups did not fit correctly into the cup holders, and he asked me to design and print a plug for the cup holders that he could insert and remove depending on the cup size.

Enter the cup holder plug!

I figured I would upload the STL here just in case someone else is facing the same issue. It was my first end-to-end design in Fusion 360, so I am humble about it, but it worked perfectly for what he needed, so I am also proud. The plug is 69mm in diameter and 14.5mm thick with a 6.5mm radius half-circle hole in the side for easy removal.

I printed them with 4 walls and 10% infill just in case they faced heavy use, but I suppose half that might suffice if you want to do the same thing. There's really no need for supports, because for the most part it is a simple cylinder, no taper. I can fit five or six of them at a time on the build plate of my Qidi X-Plus, which is pretty nice.