Hydration
Electrolytes: why water alone isn't rehydration
Sweat isn't just water. It carries sodium, potassium, magnesium and chloride out of the body with it — and the harder and longer you train, the more you lose. Drinking plain water afterwards replaces the volume but not the minerals, which is why you can finish a bottle and still feel flat.
An electrolyte blend puts those minerals back. Sodium is the one lost in the largest amount, and it's what allows the body to hold on to the fluid you drink rather than passing straight through. Potassium works alongside it and contributes to normal muscle function.
This is also why the serving goes into 500–750ml of water. A full electrolyte load needs the dilution to be absorbed comfortably — it's part of how it works.

