I've ridden with a T1D for years and he only eats fast carbs on the bike. Of course he has a meter and pump installed, so he doesn't have to stop and take his BS anymore. My reading tells me that T2D endurance athletes do the same thing, which must be trickier without the installed instruments. Off the bike or road, of course it's another story. Everything's different when you're burning 500 calories/hour - or not. Which is actually not that different from non-diabetics. I eat no fast carbs off the bike, nada.

The Diabetes Guide to Running Your First Marathon | Beyond Type 1 - be sure to read the Editor's note at the top of the page.