Combine cake mix, apple cider, melted butter, eggs, cinnamon, brown sugar, and vanilla in a bowl. Mix together until combined.
Spray cake pan with non-stick spray. Pour cake batter into pan and bake for 35-40 minutes until a toothpick comes out clean.
Remove from the oven and let rest in the pan for 20 minutes. Turn onto a wire rack over a baking sheet (to collect the extra topping).
Brush the top and sides of the cake with melted butter. Spread cinnamon sugar all over the cake by hand. Let stand for 20 minutes and then add additional cinnamon sugar.