Preheat your oven to 325°F (165°C). Grease or line (with parchment paper) two 9x5-inch loaf pans.
In a large mixing bowl, combine the starter, eggs, oil, milk, and vanilla extract. Mix well until smooth and thoroughly combined.
In a separate bowl, combine the flour, sugar, ground cinnamon, salt, baking powder, and instant pudding mix.
Slowly add the dry ingredients to the wet ingredients. Stir until just combined; do not overmix.
To make the cinnamon sugar mixture, mix together 1/2 cup of granulated sugar and 1 tablespoon of ground cinnamon in a small bowl.
Pour about a quarter of the batter into each prepared loaf pan. Sprinkle a generous amount of the cinnamon sugar mixture over the batter in each pan. (Keep about 2 tablespoons of the mixture to sprinkle on top of the bread)
Use a wooden skewer to swirl the cinnamon sugar into the batter gently. ( *** see notes below. You don’t want to use metal utensils when making this bread)
Pour the remaining batter evenly over the cinnamon sugar in each pan.
Sprinkle the additional cinnamon sugar mixture on each loaf for a crunchy, sweet topping.
Bake in the preheated oven for 1 hour or until a toothpick inserted into the center comes out clean.
Remove the bread from the oven and let it cool in the pans for about 10 minutes. Then, carefully transfer the loaves to a wire rack to cool completely before slicing and serving.