Leeford Rock On Energy Drink Powder Leeford Rock On Energy Drink Powder contains dextrose and sucrose, carbohydrates that provide instant energy and zinc, to boost metabolism and immunity. Rock-On instant energiser is sugar-free, beneficial during prolonged exercise, improves exercise performance, provides rehydration during illness and in hot environments, if repeated vomiting with diarrhea exists, helps prevent heat stroke, provides sustained energy, contributes to electrolyte balance and fights back cramping (because of lack of energy in muscles)..