It's already been proven to be ineffective on worms, however, on a worm free chicken, a LITTLE ACV in their water, helps make their system less conducive to worms getting started. It's a mild preventative at best. BUT a LITTLE ACV helps build calcium for stronger, denser bones in their formative years, just like it does to people.
NO !!!
Adding vinegar to their water? Why? Do you know what the pH of their water is, and why try to change it? A silly thing to do, IMO.
Apple cider vinegar is great for cooking and stays in my kitchen.
Mary