I'm exhausted. I have a final in less than 2 hours. What can I do to wake myself up and de-fog my brain a bit?

I have horrible insomnia. I haven’t slept more than 2.5 hours at a time, 3.5 to 4 hours a night, for over 8 days. Last night I slept less than 3 hours. Is there anything I can do sharpen my brain a bit? I’m prepared for my final, but my brain feels sluggish and I’m a bit nervous that I might choke because I just can’t focus.

Help!