Preheat your oven to 350°F and lightly grease or line a 9x9-inch baking pan with parchment paper.
In a large bowl, whisk together the brownie mix, oil, eggs, Dr Pepper, and vanilla extract until smooth and glossy. Pour into the prepared pan and spread evenly.
1 18.3 oz box fudge brownie mix, 1/2 cup canola oil, 2 large eggs, 1/2 cup Dr Pepper soda, 1 tsp vanilla extract
Bake for 30–35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Let cool slightly while you make the sauce.
In a small saucepan, combine Dr Pepper, butter, cocoa powder, and sugar. Bring to a gentle boil over medium heat, whisking constantly for about 3–4 minutes until slightly thickened. Remove from heat, stir in vanilla extract and a pinch of salt.
1/2 cup Dr Pepper soda, 1/4 cup unsalted butter, 2 tbsp unsweetened cocoa powder, 1/2 cup granulated sugar, 1/2 tsp vanilla extract, pinch salt
Slice the brownies into squares and drizzle warm Dr Pepper chocolate sauce over the top. Add a scoop of ice cream for an extra treat!