Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius). Grease a muffin tin or line with paper liners.
In a large bowl, whisk together the pancake mix, milk, eggs, and sugar until just combined. Do not overmix.
Fold in your desired mix-ins, if using.
Fill the muffin cups batter 3/4 full.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the pan for a few minutes before transferring them to a wire rack to cool completely.