Exponential decay of caffeine for popular beverages
As many may already know, caffeine stays in our system for quite some time after consumption; in fact, it leaves the body at a rate of ~11% per hour, giving it a half life of ~6 hours (#s vary slightly depending on genetics, body mass, tolerance, etc). In other words, if you drink a cup of coffee with 140 mg of caffeine at 11am, you'll still have 70mg of caffeine remaining around 5pm.
I was curious to see just how long different drinks keep us caffeinated, so I created a tool to show the caffeine remaining by hour for various popular beverages (assuming an 8oz serving size):