Sports drinks and other on-the-run fueling products such as gels, beans and Clif Shot Bloks were originally invented to supplement your energy intake. Your body can only take in so much energy in the form of sugar, and when you exceed that level, it causes nauseau and stomach upset. The idea is not to replace the energy lost while running but to only replenish some of what is lost. This, I believe has been lost in marketing translation.
Everyone will have their own unique menu for fueling on the go. Some go with sports drinks only as it contains both sugar, electrolytes and fluid and is easily digested. Others go with sports drinks plus a gel along the way. Still others go with the simplicity of water, use electrolyte tabs such as Nuun and Succeed or gels as their main source of energy. Confused yet? You should be. Endurance fueling has become as intimidating as selecting a cereal at the grocery store. Keep it simple and target to get in 30 to 60 grams of carbohydrate per hour for runs longer than 60 minutes.
If you are on the lighter side, lean toward the lower end of the range and vice versa. Practice this in training to identify which products agree with your system. Avoid mixing a sports drink with a gel or beans, as all of these products are designed at about a 6 to 7 percent sugar concentration to allow for quick absorption rates. If you mix sports drinks with a gel, this increases that concentration level and you'll develop sugar belly. You can also develop this condition if you take in too much sugar during the run. Keep track along the way, and you'll develop a recipe that works for you. Look at the carbohydrate content on the label. Aim for an hourly rate on the low end of the range, and tweak it from there. You'll avoid a lot of issues along the way and take in only what you need to replenish.