Preheat oven to 325°F. Wrap the outside of a 9-inch springform pan tightly with two layers of heavy-duty foil. Stir together graham cracker crumbs, melted butter, and sugar until the texture of wet sand. Press firmly into the bottom of the pan and 1 inch up the sides. Bake for 10 minutes until set and fragrant. Set aside to cool. Reduce oven to 300°F.

In a small bowl, stir together melted butter, brown sugar, and cinnamon until smooth. Transfer to a squeeze bottle or small zip-top bag with the corner snipped. Set aside.

In a large bowl, beat cream cheese on medium-low speed until completely smooth and no lumps remain, about 3 minutes. Add sugar and beat until incorporated, scraping down the bowl twice. Beat in sour cream and vanilla. Add eggs one at a time, beating just until blended after each addition. Do not overmix.

Pour half the cheesecake batter over the crust. Drizzle half the cinnamon swirl in a spiral pattern over the surface. Use a knife or skewer to drag through the swirl, creating a figure-8 pattern. Pour remaining batter on top and repeat with the remaining cinnamon swirl, dragging the knife through to marble.

Place the springform pan in a large roasting pan. Pour hot water into the roasting pan until it reaches halfway up the sides of the springform. Bake at 300°F for 55-65 minutes, until the edges are set and the center jiggles slightly like set Jell-O. Turn off the oven, crack the door, and let the cheesecake cool inside for 1 hour.

Remove from the water bath, discard foil, and run a thin knife around the edge to loosen. Cool to room temperature, then refrigerate uncovered for at least 6 hours or overnight until completely cold and firm.

Beat cream cheese until smooth. Add powdered sugar, 2 tablespoons milk, and vanilla, beating until pourable. Add more milk 1 teaspoon at a time if needed. Remove cheesecake from springform, transfer to a serving plate, and drizzle glaze over the top. Let set for 15 minutes before slicing with a thin, sharp knife wiped clean between cuts.