i prefer dark chocolate, i keep some in the freezer for when a quick endorphine rush is wanted. dont let tv propaganda fool you, milk chocolate is not better. the darker the better!
Actually they are quite deadly -- it takes alot of time for the sugar to finally make a dog diabetic. But caffeine gets to work right away. Caffeine accelerates the heartbeat to very dangerous levels. That's why coffee, tea, etc, are all toxic to dogs.