The guys in my group have been advising me to eat/drink some protein, and I think they also said fat, when on rides longer than 2 -2.5 hours. Would individually wrapped cheese sticks be a solution? The group seems to favor Hammer products, I'm sure that's fine but I'm trying to avoid the designer foods. For instance I eat peanut butter and honey sandwich instead of Cliff bars.
Protein is good after a long workout as it helps your body build muscle but your body isn't able to utilize it in the short time (even if it's an hour or two) from consumption to the end of your ride. Protein isn't used as fuel by the body, protein contains amino acids which are muscle building blocks. That's a very rudimentary explanation but I hope it makes sense.
Check out recipes utilizing chia seeds - those seem to be very popular with endurance athletes. I know they are gaining popularity since the book Born to Run by Christopher McDougall but I haven't taken the time to research them.