Preheat oven to 400°F. Place 12 paper or silicone liners in your muffin tin.
In a large bowl, combine flour, baking powder, baking soda, salt and cinnamon.
In a medium mixing bowl, whisk together eggs, Greek yogurt, oil, maple syrup, almond milk and vanilla extract.
Pour the liquid mixture into the bowl with the dry ingredients and stir until mixture is just combined. Don’t over-mix! It's okay if there are a few streaks of flour left.
Fold in mix-ins of choice, then evenly divide the batter into the prepared muffin tins. If you want to make a variety of flavors, divide the mixture evenly and add the appropriate amount of mix-ins. To make all four varieties, divide the mixture into quarters and add ¼ cup of each mix-in to each quarter of the batter.
Bake for 16-18 minutes or until a toothpick inserted in the center of the muffin comes out clean.
Let muffins cool in the tin for a few minutes, then remove so they don’t continue to cook and let cool completely on a wire rack.
Store at room temperature for 3-4 days or in the refrigerator for up to 1 week in an airtight container. You can also freeze for up to 3 months in a freezer-safe container.