Trying to make apple pie and turned sauce into caramel how do I undo?

I would expect that you could thin it with apple juice or even water to the texture you were looking for. Might be worth a try. I'm assuming this is the sauce that the apples go in before they go in the pie. If not, I'm not sure what to do because I'm not sure what you're working with.

Can't. The ingredients (sugar, butter, maybe cream) are now a new thing (caramel) and can't change back.
But a new (delicious) thing.
If you can't or don't want to use it in the apple pie, save in fridge for another use.

What kind of sauce was it supposed to be? And is it smooth like caramel? Because if it is, I say pour it over your apples and bake your pie - it sounds good to me!