Put the coconut oil in a mug and microwave for 20 seconds, until the oil is melted. Set aside.
In a small bowl, whisk the egg, vanilla, water, and maple syrup together.
Add the coconut flour and baking powder and whisk until smooth.
Gently stir in the blueberries.
Put the muffin mix into the mug.
Microwave the muffin for 2 minutes.
Once the muffin comes out of the microwave, it should just pop right out of the mug.