advice for boyfriend who snaps at me

Ha

My boyfriend often snaps at me for little things like today when i asked him if he was sure he didn’t want any m&ms after he said no thanks once. He has sensory issues and gets overwhelmed quite easily but i really don’t like it when he snaps at me and i’ve told him before but he says it’s out of his control. I’m really not sure what to do because even though i understand that it can be a lot for him i don’t think asking if he was sure he didn’t want any would be a problem. (even though he was driving) Does anybody have any advice? we’ve only been together for a few months but we’ve grown really close and this is the one thing that bothers me even though i try to be as understanding as possible. I just really hate when people snap at me especially when I was just trying to be nice and offer some of my snacks. Advice?

Also the thing about pineapples is cause we decided we would have code words so i could know when he was feeling overwhelmed. pineapple is when he has sensory overload and he says forcefield (cause of modern family lol) if he needs physical space