Advice ? My 5 year old is out of control !

Ok so I have a 5 year old son . Only child as of right now but we’re having his first baby sister in August. He just finished his first year of pre-k and teachers had problems with his behavior here and there bc he’s so hyper ! So we started seeing doctor and a therapist and they believe he is adhd ( witch I knew so just didn’t have it proven ) . His doctor wants to wait till he’s at least 7 to start any kind of medication , witch I am totally ok with bc I didn’t really like the idea anyway but if my son needed adhd meds then I’d want wants best for him . So here we are summer time ! And I figured I’d start baby sitting bc he’s so bored during the summer and doesn’t get to play with other kids besides school . We moved from our home town a year ago and in our home town he never had anyone to play with anyways . So I started baby sitting and he’s just so evil if they aren’t doing what he wants ! Like he punched the little boy I baby sit just to be mean because he was trying to take the little boys boots and run off . ( lots of more mean stuff like this) He gives me a bit trouble to and I’m so exhausted . He does not listen to no ! He will keep asking throw a fit and act crazy . Can’t take him in public because he wants to run around ( I know his adhd has something to do with it also ) I just need help ! It’s me and him all day long besides the little ones I baby sit witch I’m stopping this month due to our baby arriving in August . I can keep going on and on with issues but we’d be here all day 😣 I’m trying to be a great mother and not have to punish him every 45 minutes when he does something but nothing at all is working !