One of the first things you notice after opening a jar of Coco Loko is that it looks like hot chocolate mix. Snorting a line of the brown powder with specks of white confirms its familiar flavor, followed by a rush of energy. Americans are beginning to see the product alongside candy bars and energy pills at local shops as the Florida company Legal Lean moves to take a European club-drug trend mainstream. “I can see it taking off, as long as it doesn't get too controversial,” says Nick Anderson, director of marketing for the five-person Orlando company. "We feel...