Are you meant to drink water while in the sauna?

Yes. Drink water to replace the fluids lost through sweating; you can drink it before, during, or after the sauna. Huberman suggests at least 16 ounces for every 10 minutes in the sauna, while noting that needs vary with how much you sweat. 1

• 16 ounces per 10 minutes: That is Huberman’s general rule of thumb, not an exact formula. 2
• Electrolytes: Replacing water matters, and electrolytes may also be needed; needs vary with sweating and salt loss. 3 4

A pinch of sea salt is one option mentioned for adding electrolytes to fluids. 5