I am sure it is, type vinegar in the search bar thing and see what comes up, but I know I have read on here somewhere that some put it in their drinking water. Vinegar is a wonderful thing for all kinds of stuff!!!
You need to make sure you are using the ACV with the mother in it for your chickens to reap the total benefits of the vinegar though. I use the BRAGG brand that I have to get at my health food store. You will add one Tblsp. per gallon of water. It is great for the chickens and helps keep anything from growing in their water.