At my wits end with toddler eating

He’s 18 months old and just refusing to eat at this point. All he ever eats are fruits. He will eat ANY fruit you give him but nothing else. He hates bread, noodles, veggies, meat, baked goods. Basically everything but fruits and string cheese. I make him the same thing as his brother almost everyday but he refuses. Today was grilled cheese, apples and peas. All he ate was the apples and threw the rest on the ground. The only way he gets veggies is from the pouches like this

And that’s only because it tastes like fruit. I’ve tried not offering the fruit but then he just refuses to eat. He hasn’t gained any weight in 3 months. He’s petite and very active. Doctor didn’t seem worried last month but it’s so frustrating. Does anyone have suggestions for picky fussy eaters. Idk what else to I want him to eat 😭 also, he still gets 8 oz of whole milk in a sippy cup 3x a day and drinks it SO fast like within 1 minute it’s gone. Please someone give me advice I’m at my wits end