Heat oven to 350℉/177℃.
Line 2 muffin pans with cupcake papers or spray with baking spray. Set aside.
In a large bowl, whisk flour, sugar, cocoa powder, baking powder, and salt together.
Add eggs, milk, vegetable oil, and vanilla to dry ingredients.
Whisk until smooth.
Add Guinness a little at a time, stirring to combine.
Portion batter into prepared pans.
Bake 15-20 minutes, or until cupcakes test done.
Let them cool slightly then remove cupcakes and place on a cooling rack.