When I was on a trip a while ago a friend had a word for the final bit of water in a bottle. The point of the word was to emphasize the (purported) high percentage of saliva in the final sip in a bottle. The word was used in situations where multiple people had drunk from the same bottle before the final sip.
I have forgotten the exact noun, but it sounded like /ɣɝʃlɛ/ to me. I'm fairly sure it wasn't a word in original English - it may have been borrowed from Hebrew or Arabic.
I found a reddit page with a similar question for German, where one user mentions "Spuckschluck", but it's not the word I remember.