Originally Posted by thebulls
Eat a big slug of calories, wait five to ten minutes to get some into the blood-stream, then stand up and sprint like the devil is chasing you.
+1 to this. If your blood sugar gets low, sleepiness will follow. If you can continue eating, and add some sweeter items to add glucose to your system, then that should help keep you awake. Increasing your heart rate also helps keep sleepiness at bay. My riskiest times at night are on long descents, where I've stopped pedaling, and I've usually forgotten to eat because I was focused on climbing the hill that I was now descending.