Alcohol. Before getting formally diagnosed and medicated, drinking was the only thing that would quiet the inner restlessness. It worked but it's not a healthy lifestyle at all.
This is something I like to bring up to people who are hesitant to medicate their kids. Yeah, I know you think Timmy is fine because he's not completely failing in school, but you should at least show Timmy that he has options and that it's OK to talk to a doctor and take medication if he needs it. He doesn't have to rely on Jack Daniels and Folgers to eek his way through life.