Trying to get kids to eat supper and not junk food.

To night i have made sloppy joes well most of my kids like it but i do have a picky eater and her name is katelyn. she wakes up from a long nap and is cracky and is stomping her feet and trying to get her way. well that does not work here in my house and she should know that but she is checking how fast i am going to let my gard down so she can get what she wants. she wants a wagen wheel and not eat her supper then she wants to eat yogart but i said she needs to eat her supper. what is a mom to do. the other kids did eat their food but if katelyn is trying to be the boss she wants everything her way. anyways i have won this battle because she is eating her supper and is not complaining. yah for mom and one point for mom