Preheat oven to 350 degrees F (175 degrees C). Dust a 12-inch oven-safe skillet with a pinch of cake mix and set aside.
Mix cake mix, water, eggs, 1/2 cup vegetable oil, pudding mix, and cinnamon together in a bowl. Pour into the skillet.
Bake in the preheated oven until a tester comes out clean, 30 to 35 minutes. Let cool for 10 minutes; invert onto a plate.
Place chocolate drink tablets and 2 tablespoons vegetable oil in a small saucepan. Cook over low heat, stirring constantly, until the chocolate is melted and the glaze has the consistency of syrup, about 5 minutes.
Pour the glaze over the cake, spreading with a spatula. Let cool for 10 minutes and sprinkle with confectioners' sugar.
