It's hard to give a conclusive amount to put in the chickens' waterers.
Vinegar keeps water fresh and from turning green. It's also supposedly good for respiratory issues. If you have a chicken with respiratory problems, you need to get on it right away. If you wait a week trying vinegar before a small amount of the antibiotic L-S 50 from a vet, you'll lose the chicken. When you treat one sick chicken, you have to treat all of them.
Dust the chickens with wood ashes, an old-time remedy. It's one of several that work.
Tricks for baby chicks
If you have them shipped in from a hatchery, put brown sugar in the water if they're stressed. Use about a tablespoon of brown sugar in a quart of water. This isn't a strict measurement.
If you hatch baby chicks and aren't prepared with feed for them, hard boil eggs and mash up the yolks. You can also used uncooked oatmeal.
Leave questions and suggest your own remedies in the comment section.
--Dale, aka Turkeyman