I used to drink that much soda, but not in a long time. But I think it is similar. I drank some water, but not a ton. Enough for my standard karate class, but during the MMA class my mouth was completely dry. And I had a large coffee on my way to the dojo. So I'm leaning toward thinking that's the problem. I'll test it out this coming Monday by super hydrating and seeing how it goes. @Wado - It's just a headache. I mean, I was certainly sore afterwards, but the main complaint was a throbbing headache.