Preheat oven to 350°F and grease a 9x13-inch baking dish.
In a bowl, whisk together flour, sugar, baking soda, and salt. Set aside.
2 cups all-purpose flour, 2 cups granulated sugar, 1 teaspoon baking soda, ½ teaspoon salt
In a saucepan over medium heat, bring Coca-Cola, butter, oil, and cocoa powder to a boil.
1 cup Coca-Cola, 1/2 cup unsalted butter, 1/2 cup vegetable oil, 3 tablespoons unsweetened cocoa powder
Pour the hot mixture into the dry ingredients and stir to combine.
Add buttermilk, eggs, and vanilla, mix until smooth.
½ cup buttermilk, 2 large eggs, 1 teaspoon vanilla extract
Pour batter into the prepared pan and bake for 30-35 minutes, until a toothpick comes out clean.