Def. eat real food before riding, but doing nothing but sip sports drink during a long ride is just asking for trouble. Even if I have a small something before my ride, (I don't like to eat a lot, else I feel sick) I still need something after about 40 miles or so otherwise I'll bonk. I found out my limit the hard way and almost passed out on the bike and crashed at 20 mph
Sports drinks are for re-hydration and don't really provide enough calories for long rides.