Sscientist say having coffee and then a 15 to 20-minute nap is the best combination to make you feel alert.
It takes 15 to 20-minutes for the caffeine in coffee to work in the brain, according to researchers at the University of britain.
Researchers say the caffeine and sleep interact with a molecule in the brain which makes us feel drowsy.
They found that a nap that ends as the caffeine clears the brain of the molecule has most people raring to go.
15 to 20-minute nap after drinking coffee makes you feel more alert
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