My brother was similar - he would gag and pretend to vomit when parents made him eat something he didn't like. One day parents left him with me for the weekend

My brother was similar - he would gag and pretend to vomit when parents made him eat something he didn't like. One day parents left him with me for the weekend. I told him he could eat the beans I made (something he would never eat usually) or he could stay hungry I didn't care - took him like 30 seconds to start eating - difference was he knew I was serious and he couldn't get anything else. He cried to mom about it when they got back etc. but still no vomiting when he had to eat it :)