Preheat oven to 425 degrees. Line a muffin tin with paper liners and lightly spray the liners with non-stick cooking spray.
In a medium bowl, mix together the flour, sugar, salt and baking powder. (If adding fresh fruit, stir it gently into the dry ingredients until well coated).
In a separate bowl, whisk the milk, oil, eggs, and vanilla until light and fluffy.
Pour the wet ingredients into the dry ingredients. Mix gently until just incorporated.
Fill the muffin cups about two-thirds to three-quarters full. Sprinkle with sparkling white sugar, if desired.
Bake for 15 to 20 minutes, or until a toothpick inserted into the middle of the muffins comes out clean. Remove from oven to a wire rack. As soon as you can handle the muffins, turn them out of the pan onto the rack to cool completely.