As often as you want, given that it's only one at a time, though, you might have to wait. You do lose time, so it's in your best interests not to load up on water. It's not permitted in the testing room anyway. No strong-smelling lotions or perfumes, either. And no cell phones. Coughing would be bad. You can have a jacket, but it'll be searched first. Security is pretty damned high. I'll try not to get dragged away. *grins*