Pretty much anything actually
I'm veggie so I'd be having veggie alternatives/vegetarian food
That said:
Kettle - cup a soup, stock, cous cous (even better made with stock), pot/instant noodles, pot pasta, smash!
Toastie maker - anything that can be grilled basically. As well as toasties - bacon, chicken nuggets, chicken breasts, burgers, hot dogs, not sure about fish fingers as they're so soft.
Is there a normal toaster? If so get toastabags and you can cook loads in them too inc eggs and baked beans
Microwave you can cook ANYTHING in just only in certain ways/dishes
You obviously can't do stir fries or roasts but off the top of my head:
Omelette (omelettes are delicious in the micro, light and fluffy get a micro omelette maker - usually available in pound shops), poached (again micro poachers in pound shops) or scrambled eggs
Baked potatoes (you can scoop out flesh and mash for wee one)
Pasta (you could use pesto or make a tomato based sauce in the micro - just Passata/tinned tomatoes, purée and herbs and garlic)
Rice dishes/accompaniment - you could get micro rice or simply normal rice but micro boil it
All meat can be cooked in micro but I think it might be nicer grilled on toastie maker
All veggies work great in micro, but for this scenario I'd take/buy plenty of tinned as they cook quickest and can also work cold eg sweet corn
I get tinned curries and chillies as a matter of course and they're lovely, I've also just bought tinned lentil ragu but haven't tried it yet so can't say if it's nice
You can also get tinned :
Stews, pasta (Bolognese, ravioli, Mac cheese), chicken in sauce, burgers in gravy, meatballs in sauce...I'm browsing Tesco app and there's sweet and sour chicken in a tin
You can have cold meals too, salad with tinned tuna, ham, spam, corned beef... I loved corned beef as a kid!
One of my favourite meals was corned beef mash and baked beans that would be a super easy meal!
Boil kettle, beans in micro, make up smash, slice up corned beef the rest will be ready - serve
Toastie you could make breakfast toasties along idea of a fry up, or banana and cinnamon is gorgeous!
Loads of stuff you can make.
Hope you have a lovely time