Canada requires nutrition values as well as a list of ingredients.
Sun-Ripe is the brand of a carton I happen to have in the fridge (for use in stews and marinating). It is labeled 100% juice, unsweetened, not from concentrate.
The ingredients listed are apple juice and vitamin C.
Note: some vitamins in juices are ephemeral (one research paper I saw said natural C is lost within an hour of juicing); often C is added to juices to replace that which has degraded.

Looking at our orange juice, Minute Maid frozen concentrate, the contents are labeled as 100% pure frozen orange juice concentrate. Since 4 tablespoons provide 160% of daily requirement of vitamin A, perhaps some A has been added, but nothing else.
We put 1-2 tbsp frozen concentrate in a glass and mix with water- we do not mix larger quantities and store since ephemerals like fruit vitamins are easily lost.

Fresh naval oranges from California are coming into our stores now, but during part of the year oranges arriving here have been stored for some time; concentrate tastes better than these old oranges which probably have lost their vitamins.
We have considered getting a juicer for squeezing fresh oranges, but the concentrate is easier and produces less garbage (the concentrate cans are 100% recyclable).