Mix the soy yogurt with the apple cider vinegar and set aside. Put sugar, sunflower oil and vanilla extract in a mixing bowl and stir together. Add the soy yogurt and apple cider vinegar mixture and stir everything until smooth. Put the flour with salt, baking soda and baking powder in the bowl (preferably through a fine sieve) and stir everything to a smooth dough.
Pour the dough into the wells of a muffin tin lined with paper cases and bake in the oven at 170 degrees for 20-22 minutes (chopstick test!)
In the meantime, whip the margarine loose and airy, about 5 minutes. Mix in the powdered sugar in several portions (ideally through a sieve) and the vanilla extract. Add some cold water (max. 1 - 2 teaspoons) and stir everything into a creamy mixture.
Let the muffins cool and brush with the cream or spray the cream with the piping bag. Garnish with colored pearls, chocolate or other edible decorations.