5 delicious and easy Adult Bento Box ideas. Mix and match your salads, couscous or any leftovers with fruit and snacks. While Bento Boxes are great for children's school lunches, they're also perfect for adults who are busy but still want to be healthy. Putting together a Bento Box lunch in the morning is very quick and can help you portion control. With suggestions in the tray, you can fill it up with your protein, fruits, dairy, veggie and grain needs.