I went 43 miles the other day on an empty stomach but at that point stopped at a gas station because I could feel some distress coming on. My typical 32.5 mile route is about the limit if I try to ride hard, and if I ride hard enough, I need something, even if it's just some gatorade powder mixed into one of my water bottles.

On longer rides I'll eat some oatmeal a little before the ride, put some gatorade powder in one or both of my bottles, etc. Depends on the ride. On a hard 50 mile group ride I'd buy a Gatorade and a Rice Krispie treat at the 10 or 12-mile point when they'd stop at a gas station to consolidate before the A and B groups split up.

I've actually bonked at the 23 mile point of a 25 mile ride before. Surprised the hell out of me, but I was in a very low energy state from trying to lose weight hard core while also cycling a ton. I'm talking one minute I'm doing 18 mph and feeling fine, a minute later I'm doing like 10 mph and wondering if I'll make it the last 2 miles to my house.