Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.
Mix dry ingredients: In a large bowl, whisk together the vital wheat gluten, all-purpose flour, baking powder, and salt.
Mix wet ingredients: In a small bowl or measuring glass, combine the water, apple cider vinegar, and brown sugar.
Make the dough: Pour the wet mixture into the dry ingredients. Mix well until a shaggy dough forms, using your hands to bring it together. Do not knead the dough, it should just come together enough to incorporate all the dry flour.
Shape the buns: Use a knife to cut the dough into 6–8 portions, depending on how large you want your buns. Shape each into a rough ball and place them on the prepared baking sheet. (It's ok if they look a little wonky).
Add toppings: Brush each bun with aquafaba or plant-based milk and sprinkle with your desired toppings.
Bake: Bake for 25–30 minutes, until the buns are puffed and golden. Let cool on the tray for at least 10 minutes before slicing and serving.
