The Dietary Reference Intakes (that have replaced the Recommended Dietary Allowances) recommend roughly 1 gallon of water intake for the adult male and 3/4 gallon for the adult female, regardless of their height, weight, etc. I appreciate that since water needs in living organisms can NOT be precisely defined it is best to keep the guidelines as simple as possible, my sense is that the DRIs have oversimplified things a bit too much. I personally prefer the RDA guidelines that were in place before the DRIs, since the RDA hydration guidelines took into account metabolic rate in a very simple and elegant way: Link water needs to caloric needs.
We know that food is broken down in the intestine into molecules and that every molecule requires a hydration sphere around it so that it can be dissolved and transported into the bloodstream and cells. The water needed to make up all these millions of hydration spheres after each meal and snack have to come from somewhere, and the water can not be stored in the body anywhere (we are not camels); it comes from our blood, cells and interstitial fluids. In other words, eating dehydrates us by taking water from every region of the body to supply it to the calories we consume. Calories, such as sugars, in liquids (fruit juice, milk, soda) cling to much of the water in those liquids so that much of the water is not available to "hydrate" solid calories that a person consumes or hydrate their body in general. Since each molecule of sugar and protein we consume uses up to four times its weight in water in the form of hydration spheres, 1000 Calories of food, corresponding to 250 g of carbs and protein, would require 250 x 4 = 1000 g of water, which is 1 Liter of water i.e. roughly 1 Quart or Liter of water is needed for every 1000 Calories consumed. Fats form organized globules called chylomicrons in the intestine, which must also have hydration spheres around it in order to be transported into the lymph system and then the bloodstream. This discussion is not part of the RDAs.
What the RDAs say is the following (link to it HERE):
"Estimate of Requirements: The primary determinant of maintenance water requirement appears to be metabolic (Holliday and Segar, 1957), but the actual estimation of water requirement is highly variable and quite complex. Because the water requirement is the amount necessary to balance the insensible losses (which can vary markedly) and maintain a tolerable solute load for the kidneys (which may vary with dietary composition and other factors), it is impossible to set a general water requirement. Adults: For practical purposes, 1 ml/kcal of energy expenditure can be recommended as the water requirement for adults under average conditions of energy expenditure and environmental exposure. However, there is so seldom a risk of water intoxication that the specified requirement for water is often increased to 1.5 ml/kcal to cover variations in activity level, sweating, and solute load."
IN OTHER WORDS: Consume 1-1.5 Liters of water for every Calories (1000 calories is capitalized i.e. 1 Cal = 1 kcal). And since your average 1000 Calories of food already contains roughly 0.5 Liters of water, a conservative estimate of water needs comes back down to ~1 Liter / 1000 Cal of food.
NOTE that since soda, fruit juice and nonfat milk contain ~110 Cal / cup, they contain about 110/4 grams of sugars and amino acids, which use up 4 times their weight in water to stay dissolved i.e. (110/4) x 4 = 110 ml. One 8 oz cup is 1/4 quart i.e. about 1/4 Liter, which is about 250 ml. Therefore, the calories in these fluids take up 110 / 250 = 44% of the water in those fluids just to stay dissolved. In other words, you lose almost half of the hydration potential of these fluids. This is why caloric fluids do not hydrate you as well and why you would need to almost double your fluid intake if you only drank caloric beverages instead of water. This would, in effect, put as many calories of empty calories in the form of liquids into your body as the calories you are eating that you are trying to hydrate with those fluids. Hydrating with caloric fluids is then an amazingly effective way to stay dehydrated, gain a lot of body fat, or both.