Preheat the oven to 375°F. Line 12 muffin cups with paper liners.

In a small bowl, make “buttermilk” by combining the rice milk and cider vinegar. In another small bowl, combine the water and flaxseed meal and allow to thicken for 3 to 5 minutes. In a large mixing bowl, whisk together the baking mix, sugar, baking powder, xanthan gum, baking soda, and salt until well combined. With a spoon, create a well in the center of the dry ingredients.

In another bowl, thoroughly combine the “buttermilk” mixture, the thickened flaxseed mixture, and the coconut oil. Add the combined liquid ingredients all at once to the well in the dry ingredients and stir until combined. Fold in the blueberries.

Spoon the batter into the prepared muffin tins. Bake for 18 to 20 minutes, or until golden brown on top and a toothpick inserted in the centers comes out clean. Let cool in the tins on a cooling rack for 10 minutes. Remove the muffins from the tins and cool them completely on the cooling rack.

Store the completely cooled muffins in an airtight container and refrigerated for up to 3 days.