hooked, it is very interesting that the Dr. said this. I am by no means a medical expert and have no medical training whatsoever aside from basic CRP. However I have done some research based on your post. From everything I have read, it appears that Caffeine is often used to treat asthma. However as you said this was a few years back, the drink he consumed may have contained Ephedra which has since been banned by the FDA. Ephedra has been known to cause asthma attacks so it may be indeed that your son consumed this. Current energy drinks however do not contain this product anymore.

One thing I would mention, and I am in no way blaming you for what happened to your child. But people especially kids who have had asthma attacks prior to, or have a history in their families should be very cautious about the stimulants and depressants they consume, this type of shock to the respiratory and blood system can defiantly cause attacks.