The thing is, fasting is all about what’s right and important for you. There are people who will consume up for 50 calories per fast and call it ‘dirty fasting’. There are those who do nothing but water. We’re not here to gatekeep you. :) MOST people say calories break a fast but hey, this has no calories. More importantly (in my opinion, again, everyone is different), it has no sugar. I’d say you’re fine.
I heard one advantage of doing IF is the feeling of hunger. It stimulates very good cells that helo regulate the body and help for not aging ( see David Sinclair, Lifespan), so I believe just some flawoured water will not do anything bad. I know people that do IF but drink anything that isn’t too caloric, like fruit infused waterz tea, coffee, etc. Good luck
I literally bulk order DASH waters and they are the most important crutch I have for keeping me on track with fasting (alongside electrolytes, of course). I’ve done ultra-clean fasts before, just plain water, and I feel the same now as I did then - definitely getting the benefits. Enjoy your DASH!!