I lose more weight per day when I drink a minimum of 1 gallon of water. The opposite is true when I don't drink enough water because I otherwise "feel fine." Beats me as to why this is so.
I wonder if it is the feeling of satiation rather than any benefit the water is bringing for hydration.
If true it is only a minor and temporary effect because it passes right out within the hour. It seems to work on another level.
I used this technique while cutting in a previous life where I lifted frequently. I'd drink a bowl of "water soup" before bed, so that I would feel temporarily satiated and be able to fall asleep more easily. (My water soup consisted of hot water, a bit of soy sauce to add saltiness, and a bit of sesame oil for greasiness... basically I was making a minimal imitation soup stock.)