Preheat oven to 350°F. Line a muffin tin with cupcake liners.In a large bowl, whisk together the flour, cocoa powder, sugar, baking soda, and salt until combined.In a separate bowl, mix together the coffee, vinegar, vanilla extract, and oil.Add the wet ingredients to the dry ingredients and stir until combined. The mixture will be thin and slightly lumpy but don’t over mix.Spoon the batter into the cupcake liners, filling them about 2/3 of the way full. Place in oven on the center rack and bake for 18 to 20 minutes, until a toothpick inserted comes out clean.