I used coffee with my 10 year old son who has mild adhd. It worked a miracle - a difference between manageable and unmangeable. I have since found out that coffee for adhd is a common advice in Germany and is recommanded by many doctors before going down the ritalin route. My son has one or two cups a day. However, if he eats anything with food colouring in it he is terrible for two days. He is otherwise on a immaculate diet free of any additives etc.
In the 1960's my brother was diagnosed with ADHD. Caffeine was his first choice to help him, in real ADHD patients, they react to sedatives as if it is speed, and anything that causes a normal person, to be hyper caused him to calm down, coffee has been a big help in my family to my brother, and cousins and nephews. It's only part of their therapy, but it helped keep them off ritalin and other strong drugs. A cup in the morning before school and it helped alot with my brother, during the morning etc.