Oof, I'm sorry about your response to alcohol. It's so often drunk socially, that must have been unpleasant to learn.
I'm gonna split this into "facts that are definitely true" and "things that hold out in my experience of drinking too much"
Factual information: Alcohol is a diuretic, which is a class of drugs that increase urine excretion. Even weak concentrations of alcohol will do this. Alcohol works by stopping you from producing a hormone called vassopressin, which is a thing that tells you to hold onto water (it helps you keep the right concentrations of chemicals you need in your body). So, basically, tldr: you lose a lot of water to peeing when you drink alcohol.
This bit is more informed by personal experience for me: regardless of how much water you drink, if you're "drunk" you can still be losing it faster than you can replenish it. Drinking lots of water definitely helps mitigate a hangover but I have never found the amount of water necessary to prevent feeling icky and dehydrated the next day.
I think (personally) that how you experience this, like, how you perceive your body and what your feelings are when you're drinking alcohol and the following hours is highly variable, and so too may be an individual's tolerance for substances—people usually fall along a spectrum in this kind of thing? But I also know a lot of people who are like "I never feel dehydrated after drinking," and without putting too fine a point on it, I don't doubt them, but I think their perception... probably differs from what their blood test results would say, haha.