Prolonged exposure to steam and heat can lead to dehydration and dizziness.
In order to avoid this, you should get a ceramic double-wall water bottle and keep it by your side in the sauna. The ceramic lining will keep the water from heating up, and help keep you hydrated as you reach the end of your session.
You should immediately stop and leave the sauna as soon as you feel any sign of dizziness or fatigue.
Here’s the ceramic water mug we currently use inside of our Mr. Steam unit: