Which is not a function of sweat? regulation of body temperature reabsorption of essential compounds excretion of excess salts and water

The reabsorption of essential compounds is NOT a function of sweat, because chemicals in sweat are excreted onto the surface of the skin but not reabsorbed back in.
Excretion of excess salts + water IS a function of sweat, so is regulation of body temperature. When sweat, which is >95% water, is excreted on to the skin, the air will evaporate the water in the sweat into the air. This takes time depending on the vapor pressure of nearby air (humidity), speed of nearby winds, and its temperature. But the removal of sweat's water takes heat away from the surface of the body (calories), thus cooling it down.