Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan.

Whisk flour, sugar, cocoa powder, baking soda, and baking powder together in a large bowl.

Mix water, oil, vinegar, and vanilla together in a separate bowl; pour wet ingredients into dry ingredients and beat with an electric mixer until smooth. Pour batter into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 20 to 25 minutes. Remove from the oven and let cool in the pan, about 30 minutes.

Sprinkle confectioners’ sugar over cooled cake.