HOW DO U CONTROL SLEEPINESS HELP

[dadya06m174]

So... while i am writing an exam..it doesnt matter how much sleep i have gotten ,3 hrs or 12 hrs, the moment i start writing the paper , i immediately feel sleepy like i was fine 5 min ago . I even tried shit like pinching ur self or pulling my hair but that did nothing. Any tips for what i can do while sitting at my desk??