what are you eating?? focus on getting fiber. if you dont like a lot of fiber heavy foods then find a way to work a psyllium husk supplement into your day to day. it will keep you full between meals, you wont want to snack
past that, get protein, make sure to stay hydrated. i have adhd too and putting lemon, lime, orange, or mint in my water makes it much more enjoyable
if youre already getting good amounts of fiber and protein & staying hydrated, then i recommend lifting weights
adhd makes everything more difficult but focusing on your health will do more long-term than any med, supplement, etc will ever do