There are standards for the average amount of water required for the human body, however, they are rather meaningless due to different parameters of the body, habitat, type and amount of food eaten, human lifestyle, and so on.
Fluid intake is regulated by the center of thirst in the anterior hypothalamus of the brain, and the feeling of thirst causes dryness of the mucous membranes, which is why people feel comfortable immediately after drinking, although the water has not yet reached the cells. All this happens in automatic mode, so if you are thirsty, drink, you do not need to invent and count the conditional 2 liters of water per day.
There is a wonderful TV show "Adam spoils everything", where in a comic form he refutes myths, based on facts and interviews of scientists, destroys marketing ideas built mainly on advertising gimmicks and business ideas. There is an issue on this topic, and about the popularity of vitamins, a very interesting program. Recommend
Different numbers are always given, even in some textbooks on physiology there are certain ones. But the teacher said "you need to drink as much as you want," and I adhere to this position. But I do not impose on anyone
There is no single criterion on this matter. A person should drink water when he wants to. Our body knows much better how much and when :)