Caffeine is a stimulant. Faster heartbeat, more jerky motions, and slightly faster reaction times are the result. None of which enhance extended range precision accuracy, as they tend to translate directly into your trigger control, sight picture's erratic appearance, and (unless you have something to deaden it), a jumpy firearm, even on a bench.
If you must have some, tread lightly.
Otherwise, drink OJ or grapefruit juice. They both contain natural elements that "wake" us up, but in a much more gentle fashion.