Preheat your oven to 350 degrees.
In a large mixing bowl, combine the yellow cake mix, apple cider, sweetened applesauce, eggs, and melted butter using a hand mixer on low speed.
Add in the brown sugar and vanilla extract. Mix well until everything is combined thoroughly.
Grease and flour a bundt pan generously; pour your batter into the prepared pan evenly.
Place your bundt pan in the preheated oven and bake for about 40-50 minutes. Check doneness by inserting a toothpick into the center; it should come out clean.
Once baked, remove from the oven and let cool on a cooling rack for approximately 15 minutes.
Carefully turn the bundt pan over onto a cooling rack or parchment paper. Gently shake to release the cake.
In a small bowl, combine sugar and cinnamon for your topping. Brush melted butter over the top and sides of your cooled cake before sprinkling generously with the cinnamon-sugar mixture.