Designed based on an existing product. Screws onto most standard plastic bottles. Place the pill in the spout at the top and take a good chug. This helped tremendously in getting my son to take his daily medicine. He was not able to swallow pills traditionally. 

I'm leaving the original in there in case anyone wants it but does not have the O-rings to use. it does have to be on tightly and perfectly to not leak though. 

Printed at 100% infill and supports set to 85 degrees (so it doesn't try to support the threads)

* I know there are many concerns with using PLA for eating/drinking based designs. The .5 seconds it will be in use with plain water was worth the risk to me. Otherwise, this item is commercially available https://a.co/d/3R9rEuN .

V1 - Works but has a tendency to leak

V2 - uses a 24mm O-ring to fix the leak