First item to upload, and it's a simple one. Part of my 40K terrain is to make pipes come into storage containers (painted soda cans).
However, Soda Cans are circular, whilst the end of a straw is straight. This often ends up with a big, messy dollop of hot glue.

This item is a very simple box, one side is curved to fit a regular 330ml soda can perfectly, the other has a hole to slide a straw into.

I designed it in Fusion 360. I've printed it on a Monoprice Mini without any issues.

NOTE: Despite there being a "standard" straw diameter, I did find some variety. I have added the original fusion360 file here so that you can modify the diameter if needed.