Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan.

In a large bowl, mix together the mashed bananas, soybean oil, soymilk, and sugar.

In another bowl, combine the flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, stirring until just combined.

Fold in walnuts or chocolate chips if using.

Pour the batter into the prepared loaf pan.

Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.

Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.