Preheat oven to 350°F. Grease a 8x4 or 9x5-inch loaf pan with shortening or butter and coat it with sugar. You can also just use nonstick cooking spray (but if you use the spray don't add the sugar; it'll burn the outside of your bread).
Mash bananas in a large bowl using a fork or a potato masher.
Add oil, sugar, eggs, baking soda, cinnamon, and salt and stir until combined.
Add flour, milk and vinegar and stir until batter is combined (will be slightly lumpy). Pour into prepared pan.
Bake for 45-60 minutes, or until a toothpick comes out clean alongside the crack. (If you put the toothpick in the crack it will come out with just a little batter/crumbs sticking to it.) The edges will be a dark brown and there will be a nice crack down the center. (There is a wide range of cooking time because all ovens bake differently, as do all pans. My banana breads never bake in the same amount of time!)
Cool completely before removing loaf from pan and frosting.
To make the frosting: whisk powdered sugar, cinnamon, and salt in a medium bowl. Whisk in vanilla and 1 tablespoon milk, adding more milk as needed for consistency (up to 2 tablespoons). Frost banana bread and top with toasted pecans. Chill to set. Store in an airtight container for up to 3 days or slice and freeze for up to 1 month.