In short: It may not be possible to recommend any fixed amount of water to anyone, because the water needs differ from person to person, and for a given person, from day to day, which mainly depends on the extent of sweating.
According to Dietary References for Water, National Academic Press (p. 80, Table 4-2), an estimated minimal loss of water (when not sweating) in a healthy adult is ~1 liter per day, so this is the minimal amount of water one should consume (from foods and beverages combined).
Dehydration and Rehydration, Defense Technical Information Center:
The daily water needs of sedentary men are ~1.2 L or ~2.5 L and
increase to ~3.2 L if performing modest physical activity. Compared
with sedentary adults, active adults who live in a warm environment
are reported to have daily water needs of ~6 L.
According to Mayo Clinic, you can know you are well hydrated when:
- You are not thirsty.
- Your urine is clear or straw yellow.
- You maintain your usual body weight from day to day (for example, 2 liters water loss results in 2 kilograms or 4.4 pounds of body weight loss).
- The skin at the back of your hand recoils instantly when you pinch and release it (skin turgor test, MedlinePlus).