Here's my take but of course YMMV, study's show that exercising for 1.5 hours or greater is required before the use of a sports drink to replace electrolyte and carbohydrate.
For the most part when I exercise (2h/day) I usually drink plenty of water before to stay well hydrated and replenish as needed during the course of the workout and at about the three quarter point I dilute 4oz of a sports drink (carbs + potassium) with 4oz of vitamin infused water and use that to push me through till the end.
Everything is YMMV though, find something that works for you and stick with it!
I.e I train during fasted state (haven't eaten in 12-14 hours) and only take some BCAA's mixed with a low calorie orange juice 30 minutes before a workout and find I get my optimal results. My sister tried this once and vowed never to do it again!