Yes. It is a good idea. When my birds hatch I place ACV and honey in their water. The ACV alters the Ph of their systems and keeps cocci and other illnesses at bay.
I continue it into their adulthoods.

I dont believe that but am very interested in links offereng proof.

I do believe that vinegar does offer some health benefits but I dispute that a slight intake of acid would reduce the cocci load. Most of these little thing we do por our pets serve to make US feel better and dont really do a lot for the animals. As long as nothing harmful is done it seems fine but I wouldnt fall for the often un scientific old farm tales to keep top health in my flocks.

Ditto what Fancifowl said. I'm a non believer in some of the apple cider claims, but I do agree it has some benefits and in many cases can't hurt.
Brendasue

My old friend who taught me about chickens used apple cider vinegar in her chickens water.My nurse,sister in law said that vinegar is an antibacterial.The vinegar was pushed by the organic gardeners.Do you suppose they realized that it also helped keep the waterers free from bacteria and algae?Posy Pet

Do you think that it will hurt them??

vinegar wont hurt them, might be good for them even, it will rust zinc coated waterers. There are better options for controlling bacteria and algae. A product called Oxine is a good item , more efficient and a wider use. keeping utensils and pens clean is the best option.

No it wont hurt them, and there are some benefits, I just don't agree with all the claims.
Brendasue.

There isn't a medical problem that I know of that someone hasn't claimed ACV as a cure for, according to popular lore it is a panacea. I can't think of a good kind of cleaning out that ACV could do for chickens, its apple juice with out sugar, acetic acid, yeast bits, and acetobacter bits, people assume that since vinegar can be used for cleaning that it will clean out an animal, the digestive system deals with much more powerful pH swings however and can reduce that kind of effect.