I just googled it, I'm all for herbal and holistic remedies, but I personally wouldn't use it. There are controversial opinions on wether or not garlic is toxic to chickens. I feed it in small doses and never have any issues. I wouldn't feed it daily or consistently, especially with young chicks. Either way, toxic or not, its a strong herb.
I always get concerned about ACV too. Maybe temporarily for pasty butt, but long term I wouldn't do it.
Instead, I think adding herbs like oregano, lemon balm, or similar to their feed is a good idea. The herbs are immune boosting, you can't overdo it, and there's no controversial opinions on wether or not its toxic.
I sell an herbal mix containing immune boosting herbs like mentioned above on my Etsy shop, and it works great! I think adding something to the feed is better than the water, since if they don't like it, they can pick around it or toss it out. If you add it to the water and dont offer plain water with it, they could die of dehydration.
