I'm a high performance rower that uses cycling extensively to cross train (the local waterways are.....suboptimal some of the time).
When I'm out for longer rides (2-3hr) I generally run out of calories and crash, occasionally getting dizzy. I've started carrying a camel pack and some snacks (granola, GU, etc.) which helps if the pack decides to stop for a quick pitstop but its often hard to get enough calories down fast without feeling it 10 minutes later.
I never have problems within my normal training but it typically never exceeds 2.5hrs and isn't quite as continuous. Such a workout can easily burn 1500+ Cal, however.
My question is, is there anything I can eat before rides to maintain blood sugar levels so I don't pass out while trying to strike fear into the hearts of the local cyclists?