Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners or lightly grease the cups to prevent sticking.
In a large bowl, sift together the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking powder, baking soda, salt, and pumpkin pie spice. Whisk until well combined.
In a separate bowl, whisk together the vegetable oil, eggs, canned pumpkin puree, water, and vanilla extract until smooth and homogenous.
Slowly pour the wet ingredients into the dry ingredients. Using an electric mixer or a sturdy whisk, mix on low speed until just combined. Be careful not to overmix.
Divide the batter evenly among the 12 cupcake liners, filling each about two-thirds full.
Place the muffin tin on the center rack of your preheated oven. Bake for 18-22 minutes or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Remove the cupcakes from the oven and let them cool in the pan for 5 minutes. Then transfer them to a cooling rack to cool completely before frosting or serving.