Screw on adapter for water bottles for use with PEG feeding tubes. Should be printed with food safe materials, which according to this article (https://formlabs.com/blog/guide-to-food-safe-3d-printing/) includes PLA, PP, co-polyester, PET, PET-G, HIPS, and nylon-6.
The end tapers to 4mm, but can be cut shorter to the size you need.
Model prints without supports.
The author remixed this model.
Adapted to use with PEG tubes for people who cannot eat orally.