its likely you are low on electrolytes. try this - dissolve one gram of potassium citrate in one litre of water and drink that whole thing when you are in the suana. drink more if you like. potassium citrate capsules often come in 99 mg caps, that would be perfect. one cap per litre of water.
either that or mix up some master cleanse drink, then add a bit of potassium citrate to that and drink plenty. using molasses instead of maple syrup would be a good idea.
its not enough to drink water, you have to get electrolytes.