Should I drink ACV during a 48-72 hour fast?

I think you should. You can do it like 48 hours.But let's say you're doing it 72 hours, or let's say you're going longer, realize you're going to be in some pretty hardcore ketosis. And that's pretty an acidic state. So I wouldn't add the apple cider vinegar when you're too acid because you can become excessively acid. I don't think it's dangerous but I think you might overdo it.