I think all posters care meaning is this is fairly typical teen behaviour
But rather than getting stressed at people online find solutions.
What foods does he enjoy and he is likely to bother quickly preparing or grabbing himself?
I went through something similar with dd when she left school and was working shifts:
She was constantly knackered and couldn't find the energy/motivation to make herself decent pack ups or meals when home.
I'm disabled and unemployed and while I agree older teens and young adults are and should be expected to be perfectly capable of cooking for themselves, I did the shopping/planning what was bought in and I had more time on my hands to prepare and plan solutions so that she was eating more healthily
She's also disabled and her disability means she struggles with large meals anyway, certain foods cause her pain in various ways so she naturally doesn't eat them and she struggles to maintain a healthy weight as in she tends to the very slim bordering on underweight.
So I got in for her or planned and made certain things that were better nutritionally but also quick and easy for her to either grab and eat or took very little prep on her behalf
Things like:
Fruit - long life items that survived the tramp to work better than our usual softer more fragile choices - bananas (even got her one of those banana holders as a "novelty" but useful stocking filler one Christmas) apples, pears...
Veg that was either naturally quick and easy to grab and eat or was in "snack" form - cherry toms, carrot sticks, celery sticks, baby corn (can be eaten raw), cucumber sticks...
Home made soup - I like making soup and like eating it (having some tonight myself as didn't feel like having a big meal) - either it's handy in fridge for him to quickly heat up, even in a pan doesn't take long, microwave if you have one is even quicker or you could even leave it him already heated in a flask
Leftovers can also be pointed out to him as quick to heat up in micro for a hot snack/meal
Re noodles - I have noodles on occasion as sometimes I don't feel like cooking or I'm too sore to stand for very long, even things like pot noodles can be quickly and easily "boosted" nutritionally by the quick addition of tinned veggies (which are already cooked really) like tinned corn or carrots or frozen veg like peas you can add a handful and then pour the water on and they cook fine.
Also maybe entice him with novelty "gadgets" ?
I have toastabags which as well as toasties you can cook other things in too - bacon rashers, fish fingers, veggie burger patties, potato waffles, mozzarella sticks...
Microwave omelette maker might tempt him to make those, eggs make loads of quick easy nutritious dishes you could even make an oven frittata/crustless quiche when the ovens on for cooking something else and it can be eaten as a leftover in following days, even reheated in micro
Sometimes a little bribery and corruption works too!
Bet him £5 he can't eat 5 a day every day for 5 days - and you want proof! People like challenges like this.
When I say "you" if dad/stepdad is also in the home I mean he could cook/prep stuff too - lead by example as it were.
And remind him of healthy meals/snacks that are easy and he probably really likes - I reminded dd at one point she used to love beans on toast with grated cheddar and she was like "ooh I forgot about beans!" And so if I was doing a dinner with beans I'd put the other half in a pack up pot for her to take to work the next day or day after.
Once dd had the encouragement and I gave her some ideas and she was adjusting to the shifts and not quite so knackered she started coming up with ideas of her own.
Agree school dinners are shit these days! Especially if you've a kid who doesn't like potatoes especially chips!