Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius). Line a muffin pan with paper liners.

In a large bowl, whisk together the flour, sugar, baking powder, cinnamon, baking soda, and salt.

Make a well in the center. Add the eggs, sour soy milk, oil, and applesauce, and stir together. Don’t overmix.

Fold in the diced apple. Divide the batter among the lined muffin cups, filling them two-thirds of the way full.

Combine all streusel ingredients in a small bowl until mixture resembles coarse crumbs. Sprinkle evenly over muffins.

Bake for 18–20 muffins or until a toothpick inserted in the center comes out clean.

Cool for five minutes before removing from the pan and transferring to wire rack. These freeze well.