On our regular rides through the coast range, my wife and I take a break at the second to last hilltop to drink a Mountain Dew and eat a bar. This seems to help us fly along the horrid nine-mile road that enters our city from the suburbs where speed is important for safety. Since the caffeine content is well below the OP's recommendation, I guess it's the sugar that gives us that boost, not that the fifteen minute break hurts us any either.