A specific short-nap protocol for combating acute sleepiness (mid-day slump, pre-performance) without inducing grogginess.
Nappuccino: drink a caffeinated beverage, then immediately take a 20–30 minute nap. Caffeine takes about 15 minutes to kick in, timing it to hit right around when the nap ends; the combined alertness boost is claimed to outperform either caffeine or the nap alone. Falling asleep is expected within about 10 minutes of lying down.
General nap-length rule: keep naps to 15–30 minutes. Longer naps (2–3 hours) risk sleep inertia — grogginess from waking out of deeper sleep stages — which can leave someone performing worse than before the nap, at least for a while.