

Put a photograph of your boss on the desk.
This will radiate their presence and wake you up.
Your boss's face will remind you of what you have to do. Always bear in mind you could be fired at any second if you don't get the job done.
Drink coffee
Many people drink coffee to keep them awake. However, coffee can dehydrate you, too ... so have a lot of water.
Listen to music
Use headphones so only you can hear it and not disturb colleagues. Choose music with a groovy, energetic beat. Jazz, opera and soul are no good ... they can help people to sleep.
Music that makes you tap your foot or move can make you more alert.
Take a short nap
If you feel sleepy find a place to take a nap for 10 to 20 minutes after lunch. Set your cell-phone alarm to wake you up. This will freshen you up for the rest of the day.
Adjust your life schedule and meals
For example, you might try and get home and go to bed earlier. You'll get more rest. Have a big breakfast but a small lunch.
If you don't have time for breakfast, you might switch to eating six small meals during the day and eat more green vegetables for lunch. This will make you active.
Wash your face with icy-cool water
This will immediately freshen you up if all the above ideas fail.
Take a walk around the office
Sticking to your chair will make you feel more sleepy. Pretend to walk to the fax machine or visit co-workers instead of emailing them.
Source: http://women.sanook.com