One can find electrolyte additives and other "high performance" drinks at, say, an XTreme Nutrition. When I had the time to work out like a Thoroughbred we worked out no matter the temp and no one got ill.
Karbolyn (tradename of a product) and added Electrolytes will do u good. Bananas and cantaloupe also assist.
When I do "long range" mountain biking up here - still 100 degrees in the summer - I use what I used while working out on hard cardio days (see above).