adapter that lets you replace the tiny bubble juice bottle a bubble gun with something a little bigger (a small water bottle)
This thing has very thin walls, lots of overhang and is generally a pain in the butt to print. I had good success with PLA, 0.35mm nozzle, 185C, 0.1mm layer height, printing on blue tape. Printing on heated glass did not work well as the warm glass prevented it from cooling quick enough. If you don't have a really good cooling fan, it might be helpful to print more than one (or print something else at the same time) to let the layers cool.
As a bonus, the scad file is parametric and could probably be used for making other kinds of thread adapters.