I had the same problem and discovered that drinking or eating anything cold caused my core temperature to go down and I could not sweat. So I make sure that after drinking the water I exercise (my stairsteper) until I get my heart going good (for me that's 100 steps) then I get in my portable sauna and put the temp. at three for 30 minutes and then 2 for 30 minutes. That combination works for me. I tried the higher temps. too and felt like I was cooking my body.