Since caffeine is soluble at about 2 grams per 100ml of room-temperature water, or 2.2mg per each milliliter, the most dissolved caffeine that 8mL of room-temp water can hold would be 18mg; at a 1 ...

A 12-ounce can of Red Bull contains about 114 milligrams of caffeine — more than three times the amount in a 12-ounce can of Coca-Cola. Prime Energy has more: 200 milligrams in each 12-ounce can.