A friction-fit easy-grab medicine bottle topper for cat (and possibly other animals and/or human) medicine bottles.
I have some cat medicine that comes in a bottle with a snap-on cap. The top is perfectly designed to fit a syringe (the squirt down the throat type, not the sharp pointy type), but it is absolutely not designed to frequently open and close. There is no easy way to grip it except by the retaining plastic strap that prevents you from losing the lid and after a few days, that snaps off. After that you need fingernails or pliers.
I designed this oversized cap to tightly fit over the existing cap. It gives you just the right sort of leverage to pull off the cap. As a side-effect of the design, the top also provides a large surface on which to write a quick dosage reference. (But please don't mix up the caps if you have multiple bottles!)
The specific bottle this is sized for has a cap that is 14mm across and is 7mm high. Feel free to use the OpenSCAD source file to alter, if needed. The constants up top are very friendly to modification.
Just print and push over the cap. I used two extra shells and a 25% infill to make it a bit more solid than most prints. I did not have to use any sort of glue, though your mileage may vary.