Sinks remove germs from a Duplicant even if the action bar doesn't complete.
This can be exploited to have a nearly instant sink use, by temporarily emtombing the Sink when a Dupe try to use it, as shown in the steps to reproduce.
In addition, the Sink won't use the normal amount of water when using that technique, though I assume it doesn't loose any mass.
- Build that sink design.
- Check the germs from a Duplicant using it after going to the toilet.
- Notice the action didn't complete, but germs are removed, and about 2kg (instead of 5kg) of water is used.