Thanks for consulting at my virtual clinic. I have carefully worked through your case, and I can realize your health worries. Being your physician, I assure you not to worry as I will take care all of your medical concerns. you can take pedialyte during your tennis match. But it is better to have plain water it will be more than sufficient. have plenty of water frequently. or as an natural substitute try butter milk which in my practice is the best for dehydration and sports. Hope it helps. If you need further, detailed and quick assistance related to any health issues in future, feel free to ask me a question directly from my profile. Have a wonderful time ahead. Best Regards! Dr. Arunmozhi varman