“Some water is absorbed within seconds to minutes from the mouth and stomach.
After that, the sooner water is emptied from the stomach, the faster it is absorbed, since the maximum rate of absorption occurs in the small intestine. How fast the stomach empties depends on the temp of the water, with cooler water emptying out more quickly.
Absorption of water also varies depending on your level of hydration. And there seems to be mystical genetic factor as well.
But if you’re thirsty, and you drink a load of water, it’s going to be absorbed pretty darn quick”
Buck Tilton Medicine Man Backpacker Magazine