I saw Mostel in the Fiddler revival at the Winter Garden and Mostel did the "milk bit." I even think you could see a wet sleeve in the Playbill cover photo. I attached a link of it but it's hard to tell. He also made funny faces to Tzeitel's baby. I thought that was more of his clowning but I checked the copy of the published script I had and found the stage direction, as I recall.
Any, Mostel was wonderful and it was the only time I got to see him on stage. I had seen the original prod. with Harry Goz (2 of his daughters were Bette Midler and Adrienne Barbeau). Then I saw revivals with Mostel, Herschel Bernardi and Topol. Harnick thinks Bernardi was the best Tevye and I would agree. I'd also say that Topol on stage was even better than his film performance. No one was ever funnier in the dream sequence. Later on I saw Alfred Molina and Harvey Fierstein. I missed the recent revival but I think I'm all Tevye'd out (unless Hugh Jackman decides to do it😋.