At a pinch , while not as effective, you could use your normal pots ( smear some wash up liquid on the outside to make it easier to scrub off any smoke later) - they’ll work fine just need more energy to heat up but will then keep hot longer, due to thicker bases.
But parcels make from tin foil are great for things like chicken in a sauce or veggies with some butter. Or as a flat surface ( turn the edges up to hold things in) to fry wet stuff like an egg.
or tin foil trays - the kind you buy to freeze food are handy, or keep and wash a couple from supermarket quiches or “oven ready” dishes ( garlic gratin potatoes, roasted veggies, meatballs in sauces…).
be careful not to overfill these due to being flimsy, and to handle them carefully using oven gloves. But as a way to cook things that need a container or to heat water (eg while the coals heat up and aren’t ready for cooking on yet, or in the heat left once your food is cooked), they would work if you don’t have any suitable small pots. You can use either parcels or trays for cooking, but only trays to heat water.
My Cub scouts were successful cooking meat wrapped in cabbage leaves, using a potato hollowed out to bake and cook chopped carrot and onion in the middle, and use an orange with the middle scraped out to cook cake mix, all on fires, so they’d work in a bbq.
Abd don’t forget plain “shove meat or large chunks of veg on the grill or on skewers” bbq cooking.