In many Chasidishe and Heimishe Shuls - Vodka, Whiskey and the likes are known as "Yash" which is an acronym for Yayin Saraf -
יי״ש. However would it not be more appropiate to call it Yas? Then why do we call it Yash?
I would guess because it is relatively uncommon for the letter Sin to appear at the end of a word, so the "natural" reading is Yash. Or, it could be that some people thought the second letter represented "Sheichar" rather than "Saraf," and their mispronunciation caught on.