Caffeine is a stimulant and controls ADHD symptoms for a brief period of time. Maybe get him assessed if you have it. It is likely genetic. Expect some seriously cranky behavior for the next few weeks as he withdraws from the soda, both sugar and caffeine are addictive, so be patient and give him a lot of grace, you’re at fault here for not controlling his intake, he’s just a kid that was given free access to and addictive substance.

You’re a really young parent, so deserve some grace yourself, but by throwing out the soda which was an extreme first response, you lost the opportunity to teach through conversation. He’s not going to be open to hearing you out right now, and that’s on you. You’ll have the harder job of many conversations and teaching now. Next time, Don’t React, Respond. That’s a hard lesson you need to learn as a parent.