That's 1,3,7-trimethylxanthine, a psychoactive stimulant that antagonizes the negative modulatory effects of your brain's adenosine receptors on dopamine receptors, leading to the inhibition and blockade of adenosine A2 receptors and causing potentiation of dopaminergic neurotransmission.

What you got there is the world's most popular drug. And before you roll your eyes at me - the side effects?: dehydration, anxiety, insomnia, irritability, tachycardia, mania, depression, disorientation, disinhibition, hallucinations, psychosis, and death.

And you're going around drinking it like it ain't no thang.