What is sweat made up of?

Sweat is water. But it is not all water. It contains urea and sometimes lactates. It also has minerals that may include sodium, potassium, calcium, magnesium and smaller amounts of zinc, copper, chromium, nickel and lead. However, it also depends on how much of these you have in your body. If you have a high amount of these things in your body, more will escape in the sweat.