Vegan Cake Batter Blondies

box white or yellow cake mix ((I used Duncan Hines French vanilla, which is vegan))

sprinkles ((optional; look for brands that don't use confectioner's glaze, which isn't vegan))

neutral oil ((I used safflower oil))

aquafaba ((I used the liquid from a can of chickpeas))

plain, unsweetened non-dairy milk (plus more as needed (I used soy milk))