Hiro definitely have a sweet tooth, he likes eating anything that's sweet but he especially loves churros! I could picture that Opal would scold him if he eat too much when he's a kid lol. And for favorite drink he loves LOVES hot chocolate!! Hot chocolate with marshmallows and all those yummy deliciousness specifically. And of course he also like candy! He likes any kind except for the sour ones, he can't handle sourness
And for Sylvan.. She just really likes bread, doesn't matter what kind of bread it is she will eat them all with a satisfied look on her face. And for favorite drink.. she doesn't exactly have a favorite drink, she would usually just go for good 'ol tea whenever she eats at a restaurant. And Sylvan like candy but she doesn't like it when it's too sweet so she usually eats fruit-based candy or one of those coffee ones
Great, now I'm hungry :')
(Also good luck on your exam!!)