Preheat oven to 350 degrees Fahrenheit and line the muffin tin with paper liners or grease each muffin cup.
In a large bowl, combine the flour, sugar, baking soda, baking powder, ground cinnamon and salt. Add the walnuts and coconut (if using) and stir.
In a separate bowl, whisk the eggs, canola oil and vanilla extract until well combined. To this, add the grated carrot and apple.
Gently fold the wet ingredients into the dry ingredients and stir until just combined.
Evenly divide the batter among the 12 muffin tins by filling each one 3/4 of the way to the top.
Bake the muffins for 20-23 minutes, or until an inserted toothpick comes out clean.
Let cool for 10-15 minutes before enjoying. Muffins will keep well in the fridge for roughly 5 days and in the freezer for 3 months.