Preheat the oven to 425°Line a baking sheet with parchment.
In a small bowl, stir the egg replacer and water together and allow to set up for five minutes.
In a large bowl, mix together the vegan butter, sugar, vanilla, baking powder, and salt.
Stir in the egg replacer.
Next, add in the flour, stirring until well combined.
Using two tablespoons, drop the dough onto the baking sheet, leaving about 1 1/2" between them. Dough should yield 1 dozen cookies. Flatten the cookies with the bottom of glass and sprinkle each cookie with colored sugar sprinkles.
Bake the cookies for 7 to 8 minutes, until they're barely set, and a light golden brown around the edges. Be careful not to over-bake, cookies will set up as they cool. Allow the cookies to sit on the sheet pan for 3-5 minutes before moving them to a wire rack to cool completely.