So if you think about it the whole point of a "cardio" workout is to get your heart rate up, right? By increasing your heart rate, you strengthen your heart muscle and cardiovascular health. Therefore, any stimulant drug that increases your heart rate, such as caffeine, could be considered a cardio workout, right?
I understand that there are a million and a half health risks to this-- and I'm not saying it should replace regular exercise or anything-- but would it work?