In a large bowl, whisk together the flour, sugar, baking powder and salt. In a small bowl, whisk together the oil, egg buttermilk and vanilla. Gently stir in the buttermilk mixture into the flour mixture, until just combined.
Lightly spray the doughnut pan with coconut oil spray or your favorite baking spray. Fill the doughnut pan about 2/3 full – I use a pastry bag to make this easier, but it is not necessary. Drop in several blueberries into each well, nestling them into the batter. Bake for about 15 minutes or until golden. Let the doughnuts cool for a few minutes before gently remove the doughnuts from the pan.
Make the glaze by placing the blueberries, lemon juice and water in a small saucepan over medium heat. When the blueberries burst and release their juices, use an immersion blender or a blender to puree the blueberries. Whisk in the powdered sugar in 1/2 cup increments until smooth and you achieve your desired consistency, using a little more or less as necessary. Dip the doughnuts in the glaze and let the excess drip off, then dip it into the sprinkles to coat. Let it cool on a wire rack…or enjoy immediately.