My guess is that there could more answers to that Q than there are active randonneurs.

Yesterday, for the solo pre-ride of the RUSA Highpoint Region Jan-16 brevet(s), I had an IHOP Colorado Omelet. Was the only food I really needed the whole day, although I did pick up a couple snacks late in the ride (a Snickers and a couple Nutter Butters). The snacks may have helped ward off "hunger knock" or they may have just served as excuses to get off the bike for a few minutes during the final 58-miles, which were a slog into an interminable, interminable, inteminable headWIND.