My belief is that as long as you're not thirsty and your urine isn't dark you're doing fine.
Even dark urine might not mean anything.
I heard this when it was first broadcast, and found it enlightening:
https://www.npr.org/2022/09/21/1124371309/busting-common-hydration-water-myths
The written summary is pretty good, but the actual broadcast is more informative.
While we get water from many drinks, some are counterproductive re: hydration (e.g. beer/alcohol, excessively sugary, caffeinated).
Caffeinated drinks being de-hydrating is one of the myths they're busting. They say that belief is based on a study in 1928 that looked at three people.
I drink very little water. Pretty much all the water I drink comes from my Sodastream, and I keep track and have made 26 liters in the last five months, so that's a little over a liter a week. I drink more soft drinks or sweet tea, but still nowhere near 8 glasses of
anything a day. I very rarely drink flat water--I don't like it.
I just don't seem to need a lot of liquids. I thought about this thread the other day when I was mountainbiking. About 30 minutes in, I took a couple of sips from my boyfriend's Camelbak, but no more after that because we split off from each other. When I got back to the parking lot an hour after that, I had water in the car but decided to ride in circles around the parking lot while waiting for him to get back, but he got delayed and I ended up doing an extra two miles just doing leisurely riding around in the little dirt parking lot another half an hour. I could have stopped and gotten some water out of the car, but I didn't feel thirsty or want any water, after two hours of moving.
That's pretty typical for me.
Of course there have been times when I've been exercising and I get thirsty, and if that happens I'll drink something. For a few years when I was around 40, I took a hip hop dance class two or three times a week that was very intensive. I'd always take a quart of water with me and usually would finish it over the course of the hour. But I haven't exercised like that since then, and never drink water like that any more.
I remember when I used to go to Jazzercise four times a week back in the 1980s, I would stop at a convenience store on the way and buy a 39-cent 32-ounce Diet Coke with a splash of cherry coke and suck on that all during the class. (That was long before I realized diet drinks taste horrible and switched to the glories of sugar.) I drank even less water back then than I do now because fizzy water wasn't a thing.
All of which is to say people are different, but recommendations like 8 glasses of water a day don't account for that. Plus, that recommendation in particular doesn't take into account the water in food, or other beverages people might drink, and is therefore pretty bogus on its face.
Then again, I'm the one who went 12 years between teeth cleanings and was told by the dental hygienist, "Keep doing what you're doing." I seem to be pretty low maintenance, and wonder if there are other people who might be, too, but never find out because they don't look beyond the recommendations.