Preheat your oven to 375°F. and line muffin tins with paper liners.
Sift flour, baking powder, baking soda, salt and cinnamon together in a large bowl. Whisk to be sure the ingredients are combined.
In another bowl, combine the milk, eggs and melted butter.
Make a well in the middle of the dry mixture, pour the wet mixture into the well, and stir until just combined. There will be some lumps but don't over mix the batter. Add the blueberries, raspberries, strawberries and sugar and stir gently to combine.
Using a large spoon or scoop, spoon batter into the muffin cups to fill the liners (about ⅔ full). Bake for 20 to 25 minutes, until a cake tester comes out clean and the tops are nicely browned.