Drinking 2 bottles of gatorade the day before is just going to convert and store the glycogen as fat. Pre-hydrate w/water until you pee clear and drink the gatorade the day of the run.
Like someone else said, caffeine and pace yourself. I'm sure they are going to make you wear the HR monitor, so ignore the numbers (running HR is almost always higher than riding). Remember, pain is temporary but pride is forever. If you cramp on the left (leg or side), breathe out when your left leg hits the ground, visa versa for a right side cramp.