I dunno, my mouth gets dry a little bit and I take a sip, which happens often. I also keep water glass with me all day behind computer and when going to sleep and i'm kinda used to it.
I drink about 2x 250ml glasses when I wake up, 2 when i'm falling asleep, like 2 for lunch and 2 for dinner (or replace with milk), and I fill it at least 5 times daily on random times, so that adds up to 13 glasses * 250 = 3.3 litres, and that's minimum and on days I do nothing, just staying home...
Maybe I have water addiction, and I should track it precisely
Having a water glass next to bed really kind of sucks because my bladder is full every morning and sometimes losing sleep because of this, but I picked this habit up from my girlfriend a couple of years ago and now I seem unable to fall asleep if i'm > 30 minutes w/o water, mouth feels dry etc.
Edit:
I googled some and there is even a medical termin to the sensation of having a dry mouth:
https://en.wikipedia.org/wiki/Primary_polydipsia
Maybe I have some form of that then lol, need to research. I thought it was standard to drink that much