Right, back on track. Again, I'd try and identify the Gatorade ingredients that are considered essential and find a substitute. What you'll likely get is a response like "Gatorade works well," without any knowledge of why. My gut tells me it's the electrolytes and you've gotten some good suggestions in this thread for making your own substitute. I'm very low carb and do well this way. When I hydrate with more than water, I would never consider anything with carbs. For all surgery, the patient must be fasted at least since dinner time the night before. I simply eat my normal meal and hydrate with a mixture having a good source of magnesium, potassium chloride, and salt. When I donate blood, the pre-donation guidelines are to eat a good breakfast (a meal that I don't eat) and be well hydrated, so I hydrate with the same electrolyte mixture. The snacks provided after the donation are all carbs with chips, crackers, granola bars, and some sugary juices. I noticed they stopped providing sweetened (artificial and otherwise) sodas the last time I donated. I simply re-hydrate with water. I believe you can eliminate any discomfort by preparing this way the next time. All the best.