I do not use ACV. In the beginning, before I started fermenting my feed, I did use ACV. Now, they just get plain fresh water.
However, in the summer, I have given them electrolytes, especially during those first hot summer days, before they've become acclimated to the weather change.
I had a grow out pen of youngsters several years ago. They were about 9 weeks old. It was a warm day, and I noticed several of them stumbling around. My first fear was Marek's disease. But, taking the temperature into account, and realizing that I myself was dizzy from working in the heat, I realized that they could be reacting to the heat. I mixed up some home made electrolyte solution and gave it to the entire flock. Within 1/2 hour, those youngsters were acting fine again.
Poultry Nutri-Drench is my go to. I had a hen who was a moon walker. She was a wonderful layer. Any time her body got stressed: cold weather, or molting, she'd start moon walking. I'd give her a shot of PND, and that would set her back to walking like a normal chicken again. All of my chicks get PND in their first 2 weeks of life. I also give my breeding flock some multi vits for a couple of weeks, prior to collecting hatching eggs.