Preheat oven to 350 or preheat mini donut maker. In a large bowl combine flour, sugar, baking powder, lime zest, and salt until well incorporated. In a large measuring cup add vinegar and regular milk and let sit for 5 minutes.
In a separate, smaller bowl, whisk together coconut milk, egg and vanilla extract. Once mixed, whisk in melted butter and then finally the milk/vinegar mixture.
Pour wet ingredient mixture over dry ingredient mixture and whisk until just smooth. Once oven/donut maker is preheated, spray either a mini donut pan or the odnut maker with cooking spray.
Fill donut cavities 1/2 way full with batter, then bake for 3-5 minutes, or until donuts spring back lightly when pressed and a toothpick comes out clean.Carefully remove donuts from pan or donut maker and let cool while you whip up the glaze.
For the glaze: whisk together juice and powdered sugar until a thin glaze forms. If mixture is too thick, add more lime juice. If too thin, add a little more powdered sugar. You just want to lightly coat the donuts in it and for the coconut to stick to it.
Dip both sides of donut in lime glaze, then roll completely in shredded coconut to coat. Let sit on cooling rack to dry.