A 12-ounce can of Coca Cola contains 34 milligrams of caffeine and an 8.4-ounce can of Red Bull has 80 milligrams. A 12-ounce can of Prime energy, by contrast, contains 200 milligrams of caffeine.

Revenue for Prime — Logan Paul and KSI's energy drink — fell more than 70% in the UK last year. The hype around the once buzzy drink has moderated, the brand said. The company has also faced ...