I just answered this for another mom.. Even with a 2 1/2 year old it is the same..
The forcing a child to eat food he does not like can really lead to some bad food and eating disorders in the future. You are setting him up for failure, because he DOES NOT like the taste of certain foods.
Please also keep in mind that children's senses are very acute. His sense of taste is very strong. Things like cabbage can be 3 to 5 times stronger than what you smell. Coffee is a perfect example to adults. To some people it is a pleasent coffee smell while other adults, smell a cat urine odor.
Taste is the same way. To some people the taste of sauerkraut is delicious and others say it has the odor of a decaying body and cannot even imagine trying it. Black pepper to some people is a pleasant spice, to some children it is as spicy as a jalapeno.. Imagine garlic or onions!
My father used to believe in making us eat everything that was served to us. Liver was pretty spectacular memory, with the vomiting at the table, when he refused to allow me to go to the restroom to be ill.
Please consider instead of battles with food, make it a pleasant adventure. Make sure there are things he does enjoy available for each meal (all of his lunch should be things he likes, he needs the fuel to stay alert) and then introduce a very tiny portion of foods he has not cared for in the past or new food. Ask him what he would like to eat for breakfast. A sandwich counts as breakfast, a cheese quesadilla with some fresh fruit or juice on the side. Ask him what he would like in his lunch.
Ask him to be a "brave taster". For every bite of a new food or a food he has not cared for in the past he gets a sticker. No ugly faces, no ugly comments. When he accumulates enough stickers (you decide) he can win and event, or get to pick a place he wants to eat out at. Only put a small spoonful of each item on his plate as he finishes that portion you can add another portion with HIS permission. "Would you like some more carrot sticks? May I serve you some more soup?"
At our house if the dinner is not what a person wants, they are allowed to serve themselves a bowl of non sugar cereal. No big deal.
I am sending you clarity and patience.