Thirst is just your mouth being dry. Just because you’ve made your mouth wet doesn’t mean you’ve rehydrated your body. We drink a lot of things in this country that are diuretics, which puts you in the bathroom more and dehydrates you in the process. Most people if they swapped half of what they drank with plain water would spend less time in the bathroom, and have fewer dehydration health problems like headaches.
I gave up coffee, tea and anything else with caffeine, and drink water all day. No set amount, just whenever I feel like it. I fall asleep much more quickly at night.
It seems to go deeper than that.