Preheat the oven to 425 F and spray a baking sheet with cooking spray.
Pour the soy milk into a bowl and place the cornmeal in another small bowl. In a third bowl, combine the breadcrumbs, paprika, salt, black pepper, and garlic powder.
Dip an onion slice into the soy milk, then briefly into the cornmeal (the cornmeal coating should be thin, not thick). Dip quickly into the soy milk again, then dip into the spiced breadcrumbs (the breadcrumb coating should be thick).
Place on the baking sheet and repeat the process with the remaining onion slices.
Lightly spray the tops of the breaded onion slices with cooking spray.
Bake for 10 minutes, then flip and bake for another 5 to 8 minutes, or until crisp on the outside and soft on the inside.