Show them how much money they will save by getting healthier food instead of stuff that just happens to be quick and fast aka junk food. If their health and well being doesn't matter, I'm sure the amount they would save could. Get price tags, find out how much food costs per month on what you get now vs what you could get that's better. You can make food that lasts a few days easy to feed your entire family instead of ordering shit every day that costs 3x as much.