We are living in a post-applejack world. Traditional applejack was made from apple wine in cold climates by letting barrels of it partially freeze and 'jacking' out the ice. This created something that was higher in alcohol. It also left behind all of the unhealthy stuff, and even concentrated it in the smaller volume of the finished product. Traditional applejack is a fast liver-killer. It is not commercially-produced.
Since the real stuff has gone, producers have been free to call something else 'applejack.' What is sold as 'applejack' today is simply apple brandy blended with a greater amount of neutral grain spirit. As a purist, I reject all products labelled 'applejack.' I use straight apple brandy in all mixed drinks bearing the 'jack' moniker. For thoroughbred drinking, I prefer Calvados apple brandy served neat.
But, with either so-called 'applejack' or straight apple brandy, the apple wine flavor and sweetness of traditional applejack is missing. So, what if we want something closer to the original that is not as unhealthy?
Open a bottle of good cider (sparkling apple wine). For our purposes here, you should avoid any very dry bottling - if you can. Cover the opening with cheesecloth and place it in a clean, odor-free refrigerator. Position it so that it will not be knocked over. As soon as you find it to have gone flat, blend it with one-third as much straight apple brandy. If you have been forced to use a dry cider, you should consider adding a little bit of organic, unfiltered apple juice.
That is probably as close as you can come to traditional applejack without breaking any law.