I don't have hypoglycemia, but I am diabetic (I wear an insulin pump) and I have to take in carbs to stay level during any ride longer than maybe 15-20 minutes, even when I reduce how much insulin I am getting... if I don't I will go low, and very severely.

Things I like for staying up during a ride when I am already low-ish.. half strength gatorade, sipped throughout the ride (I also carry nuun, so I have a carb-free option), as well as using GU and other energy gels (I usually down one before getting on the bike, then again every 30 minutes or so). I also carry fast acting carbs with me but rarely need them. GU is actually more long-acting carbs than fast, which is why it works well, but it has the benefit of not being filling and easy to get down quickly.

Any low-GI bars like Clif or Luna can work well before/during a ride too... however I tend to get nauseated if I eat too much right before riding, or during, so I try to avoid that if I can.

I "try" to take in about half the calories I am burning as carbs through the ride, and that works for me.