Preheat the oven to 350 degrees F (175 degrees C). Spray a 10x15-inch baking dish with cooking spray. Combine sugar, oil, and eggs in a large bowl; beat with an electric mixer until combined. Mix in pumpkin. Sift together flour, cocoa, pumpkin pie spice, baking powder, baking soda, and salt in a separate bowl. Add to the pumpkin mixture until just combined; do not overmix. Stir in chocolate chips. Pour batter into the prepared pan. Bake in the preheated oven until a toothpick inserted into the center comes out clean, 25 to 30 minutes. Let cool completely.