A stimulant drink is a beverage formulated to increase alertness and energy, usually through caffeine and often combined with sugar, B vitamins, taurine, and herbal extracts such as guarana or ginseng. Energy drinks are the best-known category, marketed to students, drivers, and athletes, while strong coffee and certain teas serve the same purpose more traditionally. A typical energy drink can contain as much caffeine as two or three cups of coffee, plus large amounts of sugar. Concerns focus on overconsumption — rapid heartbeat, anxiety, and disturbed sleep — and on marketing to children and teenagers, which several countries have restricted. Food labelling rules generally require the caffeine content to be declared.