I fill a 1.5L bottle up first thing in the morning & after 9am i start filling a tall glass (I can't give up my morning cup of tea)!
Then, everytime i drink from the glass, i fill it back up, it seems to help as you see the level dropping in the bottle.
I can usually empty the bottle by teatime & then i go back to cups of tea again as i find i get too bloated if i drink plain water before bed.