Devil Mountain's Black Label coffee has the record for the highest caffeine content in the world. The caffeine content of this coffee is over 1,500 milligrams per serving.  The UK-made Very Strong Coffee makes use of 100% Robusta coffee beans, which have naturally high caffeine content. High-Voltage Coffee comes from Australia and makes a dark-roasted blend of sustainably sourced beans. The company's website claims it's lab-tested to make sure it's high in caffeine.  The caffeine levels here are almost frightening, but if a caffeine addict in need of a caffeine fix, Black Insomnia is probably for you. A serving of this product contains more than 1,000 milligrams of caffeine.