Stomach Bug

S

So my son has a stomach bug and has been vomiting. He also has autism although he’s very mild on the scale. The thing is he only eats certain things and would rather starve then not eat his normal stuff. I don’t want to upset his stomach by offering normal food. I was offering him buttered toast because he won’t eat plain toast and my mom flipped out saying I was going to make him more sick. I don’t know what to do.. I want him to eat but I don’t want to make him sick. Will buttered toast really upset his stomach that badly? For those of you who have kids with autism, what do you offer them when they’re sick?