@Trinice, now I'm confused.
Perhaps I misread, however, I thought you asked how much condensed milk to add to your peach juice to thicken it and if you should reduce the sugar.
Later, you stated you do not, "in the real world", thicken anything.
IMHO, the dichotomy illustrates a naivete concerning cooking that might call into question other aspects of the food truck business.
First, do you want to thicken your peach juice or not?
If you do, you might...