There's a ride here in Texas called the Hotter-than_Hell 100 (100 miler). This year I did it, and the weather man said the high for the day was 114 F. For me on hot days I really need more than water or I bonk totally from losing salt. I usually have about 2/3 of my fluids as water, and the other third as Gatorade or something like that. You may try taking in other liquids to replace the electrolytes lost.