Preheat the oven to 350°F (175°C). Line a cupcake tray with cupcake liners or lightly grease each cup.
In a medium bowl, combine milk and vinegar. Let sit for 5minutes to curdle slightly.
Add both sugars, oil, and vanilla to the milk mixture. Use a whisk to mix until the sugar is mostly dissolved.
In a separate large bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture. Use a whisk to mix until smooth and lump-free.
Pour in the hot brewed coffee or boiling water and mix until fully incorporated using the whisk. Gently tap the cupcake batter to remove some air bubbles.
Fill each cupcake liner almost full with the batter using a ladle or ice cream scoop.
Bake for 13–15 minutes or until the tops are firm and a toothpick inserted comes out clean.