Preheat oven to 375°F (190°C) and line a muffin tin with paper liners.
In a bowl, whisk flour, sugar, baking powder, baking soda, and salt.
In another bowl, beat eggs, oil, milk, and vanilla extract.
Pour wet ingredients into dry ingredients and mix until just combined.
Gently fold in diced mango, crushed pineapple, and coconut if using.
Divide batter evenly into muffin cups, filling about ¾ full.
Bake for 20–22 minutes until a toothpick inserted comes out clean.
Cool in the pan for 5 minutes before transferring to a wire rack.
