After years of relying on Gatorade, I started getting nausea and gastric discomfort with it. I then moved on to a
generic Pedialyte. Months later the same issue came up, so now I rotate different brands (seems to help). I too assumed it was the sugar.
I'm assuming you drink Gatorade for the sodium, so here is everything I have tried.
I started taking salt tablets (CMC are 1 gram NaCl, which is close to 400 mg of sodium) instead of relying entirely on electrolyte drinks.