Sport Drink Gimmicks and Food Allergies
A lot of sports drinks contain very little actual water and have lots of sugar, acid, an food coloring known for causing irritation like stomach cramps. It's not uncommon to run across fruit juice drinks that have little zero actual fruit juice as well.
I used to drink sports drinks until I recently found research that pointed out issue I was personally experiencing such as tomach cramping. One of the main irritants is food dye "Red # 40" or Yellow 6. You even have some products with multiple irritants.
Here is an artical about Gatorade for example but this is not limited to Gatorade: GATORADE Low calorie Fruit Punch | Dye Diet
Artical concerning food coloring and upset stomachs: Can Food Dyes Cause Stomach Aches? | LIVESTRONG.COM