The vitamin with electrolyte powder I use for first few days after hatching. People also use it with shipped chicks. Basically hatching and shipment of chicks takes a lot out of them. What they need is to eat to gain strength. That's what the vitamin with electrolytes does, gives them an energy boost so they do eat and regain strength. It's a preventative measure. If a chick is too week to feed then it wastes away very quickly.
There is no need to put anything in the water but I do recommend mixing up a packet of the vit. with electro. if your chicks are coming to you in the mail. If your getting them at a local feed store then there's nothing they need. Just pick out the most active ones to buy.
Some folks use cider vinegar with mother. There are threads here claiming all sorts of benefits. It should NOT be used on a daily basis and the only reason people say organic is in that form it always has the "mother" in it. That's what's important if used is the vinegar still has the mother. Heinz makes cider vinegar with mother that is reasonably priced. The other goto somewhat reasonable brand is Bragg's that happens to be organic.
Think of vinegar or any other water addative as a tonic and not a sole drinking supply. Use sparingly. For instance vitamins with electrolytes we use for the hottest times of summer. In the heat animals don't feed as much just like us. Few electrolytes and they'll consume a bit more to stay healthy. The feed is what's most important. And there is nothing better for you than pure water on a daily basis.
You said about ACV; "it should not be used on a daily basis" I am curious as to why you say this?