In a medium bowl, stir together the sugar, milk, oil, egg and vanilla. In a separate bowl, combine the flour, baking powder, cinnamon and salt. Add the dry ingredients to the wet ingredients and stir until just combined.
Fold the diced apples gently into the batter.
Pour the bread batter into a greased 9"x5" bread pan. Bake at 350 degrees for 50-60 minutes. A toothpick inserted in the center of the bread should come out clean. Allow the bread to cool for 10 minutes, then remove the bread to a wire rack to cool completely.
To make the glaze, combine the powdered sugar and cinnamon in a small bowl. Add 3 tablespoons of heavy cream. Mix until it is smooth. Add more heavy cream, one tablespoon at a time, until the glaze is thin enough to spread or drizzle (whichever is desired).
Once the bread is cool, spread the glaze on top of the bread. Slice and serve.
Store the bread in an airtight container in the refrigerator.
***The calories shown are based on the bread being cut into 10 pieces (and all of the frosting used), with 1 serving being 1 slice of bread. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.