Get a pack of Think Gum "Brain-Boosting" Chewing Gum for Free.
The gum is sugar-free, caffeinated and has Ginkgo, Bacopa and Vinpocetine in it to really get your brain cells juiced up.
Use the code "FreeGum" http://thinkgum.com/
to get a pack of gum for free or $2 of a larger order.
You do have to pay shipping and handling of $1.50 on the free gum though.