Preheat the oven to 350 F. Line a 12-cup muffin pan with papers.
In a large bowl, combine the flour, sugar, baking powder, baking soda and salt. In a medium bowl, combine the coconut milk, avocado oil, vanilla and cider vinegar. Let stand for 5 minutes, then whisk and pour over the flour mixture.
Scoop a scant 1/4 cup batter into each cup, then drop in 3-4 strawberries, dividing them evenly between the cups. Dollop and remaining batter over the berries.
Bake for 20 minutes, until a toothpick inserted into the center of a cupcake comes out with no wet batter attached. Let cool on a rack.
When cooled, place the Margarine in a large bowl or the bowl of a stand mixer. Use an electric beater or the batter paddle to cream the fat, then add the powdered sugar and mix on low until it starts to form a very thick paste. This is helpful for working out any lumps of sugar. When smooth, add vanilla, mix, then add coconut milk a tablespoon at a time with the machine running on medium, just until light and whipped looking. test for spreadability, you want it to be firm enough to hold its shape, but creamy enough to pipe.
If desired, transfer to a piping bag fitted with a star tip. Pipe generous swirls of frosting on each cupcake. Sprinkle with flavored sugar, if desired.
Keep, tightly covered and refrigerated, for up to 4 days.