Why do you guys give your chickens apple cider vinegar?

Same reason I drink it. Urinary tract cleaner. flushes the Kidneys.

It also kills bad bacteria in the body.

You'll get varying answers here. 

Personally, I do add it.  I started adding it to our spring 2011 chicks when 9 of them (all Iowa Blues) came down with pasty butt.  I Googled what to do with it and found my information here... since I prefer to use natural methods over medicinal ones, I decided to give it a try.  It worked wonders for them!!  I forgot to add it to their water a couple of times and the pasty butt came back - added the ACV back to the water again and it stayed away. 

Anyway, the many [alleged] additional reasons to add it is that it's supposed to help lower the pH balance of their digestive system, increases egg production, kills germs that cause respiratory issues, keeps the slime down in the waterers, keeps the harmful bacteria down in the waterers, etc, etc, etc....

raw apple cider vinegar is nutritious and works as a general tonic. I have used it on ducks who were a bit under the weather and they perk right up. I put a couple tbsp per bucket.

That is a good idea and something that I need to be doing for my flock. How often it is advised to put apple
cider vinegar in their water. When needed, monthly, weekly? Just wondering.

Is it about 1 TBS per Gallon? What radio is best?

Thanks.

Make sure its Raw unfiltered,  I use Bragg Organic Raw - unfiltered Apple cider vinigar.  One tablespoon to a gallon of water or 1 tspoon to a quart.  I was giving it daily in their waters but have cut back to a few times a week.  How often do you all give ACV in their water?  Never was sure how often to give it.

Ok, thanks that help a lot. I will start doing that for my flock.

Where do you get raw unfiltered cider???
Thanks