DS1 is a good eater, enjoys a good range of food and lots of it.
Whilst I don't claim his diet is perfect (far from it) I don't think it's too bad.
Breakfast will typically be porridge or eggs and he has a proper home cooked dinner with lots of veg in the evenings. If he needs a snack at home it will often be cheese on toast.
But, the lunchbox. I long ago gave up putting fruit in, it's pointless, it just comes home ruined, so I now put plate of prepared fruit in front of him when he's on the PC when he gets in. It seem ridiculous to be peeling oranges and slicing apples for a 13yo but 2-3 pieces disappear in no time, where as if I ask him if he'd like some, or leave it out in the fruit bowl for him to help himself, he'd never touch it.
So the lunch box, he has a wholemeal (sandwich, cheese, pate, fish) and some homemade cake and then he likes some snacks for break etc. He'd like crisps everyday. I resist that but I doubt my efforts are any better TBH. Things like a sausage roll, pastie or scotch egg, piece of cheese or another cake. What's better but still OK in peer aware 13yo land? There's no point me putting in anything too "different", it wouldn't be touched.