Pour the apple cider into a saucepan and simmer it over medium-high heat until it shrinks down to about half a cup. This usually takes 10 to 15 minutes, and you'll notice it thickening slightly as the water cooks off. Let it cool completely before adding it to your batter.
Pulse the graham crackers in a food processor until they're fine crumbs, then stir in melted butter and brown sugar. Press the mixture firmly into a greased, parchment-lined springform pan, pushing it partway up the sides. Bake it for about 12 minutes so it sets before the filling goes in.
While the crust bakes, stir together brown sugar, flour, cinnamon, melted butter, and a splash of apple cider in a small bowl. This thick paste is what creates those cinnamon ribbons running through the finished cheesecake. Pop it in the fridge to firm up while you make the batter.
Beat the room-temperature cream cheese and sugar together on high speed for a couple of minutes until completely smooth. Scrape down the bowl often here, since any lumps of cream cheese left behind will show up as cracks later.
Mix in the cooled reduced cider, sour cream, and vanilla on medium speed until the batter is silky. This is where all that concentrated apple flavor gets locked into the cheesecake itself.
Add the eggs and mix only until combined on low speed. Overbeating at this stage adds too much air, which can cause the cheesecake to puff up and then crack as it cools.
Pour the batter over the cooled crust, dollop the cinnamon filling on top, and swirl it in with a knife. Set the pan in a water bath and bake at 325°F for 70 to 80 minutes, until the edges are set and the center still has a gentle jiggle.
Turn off the oven, crack the door, and let the cheesecake sit inside for 30 minutes before moving it to a rack. Once it's fully cooled, wrap it and refrigerate for at least 6 hours, or ideally overnight.
Brush the chilled cheesecake with the butter-cider mixture, then coat it generously in cinnamon sugar. Slice with a warm, clean knife for neat pieces every time.