The issue isn't necessarily water ingestion, but that alcohol messes with the body's ability to absorb it to where it's needed. If you're consuming high amounts of alcohol and water, and enough alcohol nonetheless builds up, the ability to absorb water goes down. It's one reason why you pee more when drinking.
I could see drinking water, then sobering up, and going to sleep could mean water could then be absorbed. That may limit the effects of the dehydration and therefore the hangover.
Also your body's overall health and efficiency probably pays a role. In my teens/20s I could get sloshed and wake up with merely a vague discomfort. In my 30s I started to get actual hangovers. In my 40s its now just awful almost no matter what I do.
On the plus side, I'm saving money drinking less in general...
I could see drinking water, then sobering up, and going to sleep could mean water could then be absorbed. That may limit the effects of the dehydration and therefore the hangover.
Also your body's overall health and efficiency probably pays a role. In my teens/20s I could get sloshed and wake up with merely a vague discomfort. In my 30s I started to get actual hangovers. In my 40s its now just awful almost no matter what I do.
On the plus side, I'm saving money drinking less in general...