For your urban travel, consider adding one or more wide-mouth thermos bottles. Add hot water and whatever ingredients you want to cook [noodles, instant soup] to a thermos, close it up and wait [minimum time will vary with size of thermos], and you can wind up with reasonably hot and cooked stuff. I use a travel mug type thermos to cook pasta or oatmeal all the time, even when camping; fill it and forget it until I want to eat.