Some great advice from the blog "The Stir" on how to neat the Afternoon Slump without reaching for the power drinks.

1) Run Up the Stairs. Or around the block, or in place. You'll give your brain a jolt and your blood will start pumping.
2) Have a Snack. Instead of chowing down on a big lunch, snack throughout the day to keep your energy levels steady.
3) Hit the Water Cooler. Sometimes when you're feeling sleepy, you're actually dehydrated. Water is the best way to keep your body feeling great and awake when it really needs a drink.
4) Skip the Booze. Just don't reach for the booze if you're feeling tired and thirsty. And if you feel rundown on a regular basis, avoid alcohol as much as possible to sleep better and stay energized.
5) Meditate. No, not a nap. Just a time out to clear your head. Whether it's five minutes or half an hour, your brain will be recharged and you'll feel refreshed.
6) Get Outside. Oxygen is a natural stimulant and you will get drowsy if you're just sitting slouched over your desk, shallow breathing. Take a walk outside and breathe deep for an instant pick-me-up.
7) Make a List. The next time your afternoon demands a nap, make a to-do list instead. Seeing everything you have to do in black and white can help you feel more in control and give you the boost to get back to it.
8) Reach Out and Touch Someone. Connecting with others through a stimulating conversation is a fast way to re-focus and wake up.