We live in a warmer climate, so yoghurt needs to be frozen and then kept in with an ice pack to keep safe... I make jelly for my older ones and just pack an ice pack with them. Frozen grapes & sliced watermelon is fantastic. We send salad cups (those smash/nude food containers are great) with lettuce, baby spinach, cherry tomatoes, cucumber , carrot, olives, etc. ham & salad sandwiches & wraps go well. In winter we send mini thermos containers with heated up leftovers from dinners (lasagnes, pasta bake , chicken noodle soup etc).