Preheat your oven to 180°C (350°F).
In a mixing bowl, combine the dairy-free milk and apple cider vinegar. Let this mixture sit for about five minutes.
In another bowl, whisk together the self-raising flour, cocoa powder, caster sugar, baking powder, and bicarbonate of soda.
Pour the wet mixture into the dry ingredients along with sunflower oil. Stir gently until everything is just combined.
Line a muffin tin with cupcake liners and pour in the batter until each liner is about two-thirds full. Bake for about 20 minutes or until a toothpick comes out clean.
Prepare the frosting by beating together dairy-free block butter and icing sugar until fluffy. Add aquafaba gradually until you reach your desired consistency. Mix in crushed Oreo crumbs.
Once cooled, generously frost each cupcake and use Oreo cookies to create bat wings.
Melt some dairy-free dark chocolate and drizzle it on top or add white chocolate buttons as eyes.