Preheat the oven to 350°F/175°C. Line a muffin pan with 12 cupcake liners and set aside.
Sift or whisk together 1 cup flour, 1 cup sugar, 1/3 cup dark cocoa powder, 1 tsp baking powder, 3/4 tsp baking soda, and 1/2 tsp salt in a large bowl. Set aside.
Into a separate, large bowl, add 1/2 cup warm water, 1/2 cup sour cream, 1/4 cup oil, 1 egg, 1 tsp vanilla, and 1 tsp instant espresso and whisk together until combined.
Add the dry ingredients into the wet ingredients and mix until just combined.
Divide the batter evenly between the cupcake liners (they should be about 3/4 full) and bake for about 20-22 minutes, or until a toothpick comes out with a few moist crumbs. Remove the pan from the oven.
Let the cupcakes cool in the pan for 10 minutes, then place them on a wire rack to finish cooling. If you're in a rush, place the whole pan in the freezer for 30 minutes to accelerate the cooling process.