Drinking extra fluid in the days leading up to an athletic event

Drinking extra fluid has many advantages (not only one):

Good regular hydration helps to regulate body heat and to compensate for sweat losses during an effort. When you sweat, you lose water but also Sodium and to a lesser extent other minerals such as Potassium, Magnesium, Zinc or Copper. This Sodium is necessary since it improves hydration by optimizing cellular exchanges.

It is also important to drink regularly, and this from awakening (not only in athletic events), to restore our blood to its normal consistency. After ingestion of water, it is absorbed by the intestines and then reaches the bloodstream. The water then mixes with the blood and dilutes the clotting factors. With less viscous blood, cardiovascular risks are limited.

it creates acid rain