So experts say: a man needs at least 2 liters of water per day. Normally this amount depends on many factors: height and body mass, temperature, physical effort, the food.
A man with a height of 1.63 m and a weight of 57 kg will need less water than a 2,15 m tall and weighing 120 Kg. Can not uniformity of the need for water. (It's like I have a mouse and an elephant. 2 liters of water? Mouse will not drink that amount and the elephant will die of thirst.)
Temperature - cold days when a man would not feel the need for more water, but the hot weather is different.
Effort - physical effort a man makes the need for water (thirst) is much higher than for a man who is sedentary.
Food - a food that consists of soup and salad will bring a minimum water needs, but a solid food and full of spices will increase the need for water. So: 2 liters of water per day are useful as standard, but it depends on each person. Most importantly, be water not beer or soft drinks, thirst is covered only by water.