Preheat an oven to 350 degrees F (175 degrees C). Lightly grease two 8.5 x4.5 inch pans. Mix together the eggs, soy milk, brown sugar, oil, and mashed bananas in a bowl until evenly blended; set aside. In a large bowl, stir together the whole wheat flour, baking powder, salt, and cinnamon; pour in the egg mixture, and stir just until combined. Divide batter into prepared pans. Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 55 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack.