Kids like to eat what they know. They usually dislike everything they don't know.
I insist that my kids have to try everything before they say that they do not like it. But if there is something that they really don't like, then I don't force to eat them. Fortunately, they like rice, pasta and potatos. And I usually make one of those as garnish. So If the kids really don't like the other food, they get rice with ketchup or pasta with tomato sauce... And the other food is for the rest of the family. But actually.. the more often the kids see you eat something while they eat just boring plain potatos, the higher the probability that they try and actually like it.
If I have a child as a guest, like my niece or my nepewwho come visiting every nw and again, I usually ask what they like before I go shopping for food.
If it were my kid I wouldn't make anything else and tell that they will eat whatever is on the table or they dont eat at all. That's what my mom did to me, and now I'm not a picky eater :)
But if you're babysitting I don't think that's a good idea because the mom probably won't like that. So just ask the kid what they want and make it for them. Then when you can talk to the mom ask her about the situation so you know how to handle it next time. It's good to reinforce rules that the mom does when she handles it herself.
Well maybe he/she doesn't like the food you have prepared, maybe you could try varying the lunches a lil or make it more fun. Furthermore, you could refuse to make him/her anything else and so they have to eat it. Or you could even find ways of making the food you have made fun, cut sandwiches in cute shapes or even if they see you eating the food they will be encouraged to do so themselves. alternatively you could Slap the l!ttle bitch and tell it to be grateful, (dont actually do that haha)
You're the parent, unless he/she is allergic to the food tell them there's nothing else so they have to eat it!
It might seem harsh at first but establishing disipline in the long run makes alot life easier/makes them more respectful. Right now they're refusing to listen to something small but if you keep giving in what happens 10 years time when it's something more serious?
sometimes tough love is the best love, you can do it!:)
Don't give in, they'll eat when they're hungry.