Wat should a 4 year olds diet consist of?

That's a lousy diet for anyone, especially a 4 year old. The problem here is, he's not your kid. I hate to break it to you, but there's nothing you can do. When you have your own kid, you can be a good mom, but you can't stop her from screwing up her own kid. Some people are just selfish and dumb and they feed their kid whatever is easiest in the short-term. Sure, feeding him junk is easy, real easy, so that's what they do. The kid is going to have health problems and behavior problems as a result, but she can blame that on whatever and continue on as is. It sucks, but it happens. It's not technically child abuse, so moms are free to do this.