Preheat the oven to 350°F and grease two 8- or 9-inch cake pans with oil. Line the bottoms with parchment paper rounds to prevent sticking.
Whisk the flour, cornstarch, baking powder, salt, and sugar in a large mixing bowl until thoroughly combined.
Add the oil, soy milk, apple cider vinegar, and vanilla to the bowl. Mix with a large spoon until just combined, taking care not to overmix. Fold in 1/2 cup of sprinkles.
Distribute the batter evenly between the prepared cake pans and bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.
Cool the cakes in their pans for 10 minutes, then remove them and transfer to a wire rack. Allow the cakes to cool completely before frosting.
Prepare the Vegan Vanilla Frosting. Frost the cooled cakes as desired, top with additional sprinkles, and serve.