I am not diabetic either ... I'm actually the opposite: hypoglycemic.
However, as a general guideline it is recommended that on rides over 2 hours we should consume approx. 250-300 calories per hour. That 250-300 calories can come from whatever sources that work for us, and since we are all individuals, we all tolerate different things in different ways.
Some suggestions:
-- energy bars - there are other brands besides Powerbars out there. My suggestion would be to go to your local LARGE grocery store and take a look at what they've got on the shelves. Mine stocks probably 20 different brands each with at least 5 different flavors, so quite a good selection. Pick out several that look tempting and fit with your diet, then take a variety on your rides so that you do not eat the same bar twice in a row. Experiment! You might find that some do not work for you, and others are great.
-- cereal bars/granola bars/fig newtons, etc. - if you can eat those, give them a try.
-- nuts - if you are not allergic or intolerant to those, bring a baggie with you on a ride and eat them as you ride. I keep salted almonds in my bento bag when I ride so that I can eat them on the go.
-- fruit - fruit is all right except that it doesn't have much in the way of calories. A banana is only 80 calories and so you'd need to eat three of them each hour which could get a little much pretty quickly. But fruit can be good for some variety.
I like to stop at least once for a meal on most of my centuries, so if you head up to that distance, and if you decide to stop for a meal, choose things that have a low glycemic index.
I hope some of this helps!
