Mix the dry ingredients in a bowl: flour, sugar, cocoa, baking soda and salt.
In a separate bowl, mix the wet ingredients: coffee, vinegar, oil, vanilla and egg
Add the wet mixture into the dry mixture and mix to incorporate.
Put cupcake cups into the cupcake tray. Add the mixture into each cup to fill about 2/3 of it.
Bake in a pre-heated oven at 350 degrees F for 22 minutes. Check doneness with a toothpick. Wait 5 minutes before removing them from the cupcake tray.