Preheat oven to 425 degrees.
Spray a 20-cavity or a 12-cavity donut pan with cooking spray.
Set aside.
In a large mixing bowl, whisk flour, baking powder, baking soda, salt and granulated sugar.
Set aside.
In a medium sized mixing bowl, whisk the milk, sour cream and eggs until smooth.
Whisk in melted butter, canola oil and vanilla.
Pour the butter mixture into the flour mixture, adding the blackberries, and stirring very gently, just until combined.
Do not overmix.
Batter will be very thick.
Spoon batter into a large zip-lock bag.
Trim a corner off the bottom of the bag and pipe batter into each donut cavity.
Fill each cup 3∕4 full.
Bake for 10 minutes at 425 degrees or until the edges are lightly browned and a toothpick inserted in center comes out clean.
Remove from oven and cool approximately 2 minutes on a cooling rack.
Remove donuts from the pan and dip in vanilla glaze.
Invert and place donuts on cooling rack.
Set out on wire racks until icing sets, approximately 10 minutes.
Serve.