If you are fatigued at mile 70 then either you are pushing yourself farther than you have before (which is a good thing to do) or you didn't eat enough. The 4 calories in a 5-hour energy shot is not enough to help you at that point.

Without knowing more info about you, your diet, your fitness, your riding, etc. my suggestion would be to eat or drink something with calories before you get to a fatigued point at mile 70. Bars, gels, drink mixes, bananas, fruit, a sandwich, baked potato, fig bars, etc. If you want caffeine there are a number of gels and bars that have caffeine in them.