It’s easier than you are probably thinking, most that are labeled as 100% juice are preservative free. Look in the juice aisle next time and you’ll see it’s many or perhaps even most of them if they’re actually sold as juice and not some kind of flavored soft drink. The ingredients and label will make it pretty clear, if it doesn’t have any ingredients listed other than juice and maybe sometimes water you should be good to go.

In my experience you also need to do some extra things to get good cider though. You need to use cider-specific yeast and add yeast nutrient, and it needs to ferment cool. Stabilizing the end product (which will usually be bone dry) so you can add a bit of sugar (I recommend dark) also makes for a better, more apple-y flavor. All that said, you can make something drinkable even with a lot less care than that. Cider is fairly forgiving.