Your body is tuned to maintain the same constant temperature, 37.0°C. When the body´s temperature is rising above that level, it cools itself down by sweating. The sweat conducts the heat out of the body faster, by evaporating from the body.
To produce the sweat, the body needs water. When the body´s water supply is getting low the body stops sweating. This increases the body´s temperature, because it is harder for the body to cool down, and increases the risk for heat stroke. Alvogen ORS keeps you from getting dehydrated, and therefore can help prevent complications like heat stroke.