In a large bowl, mix the sugar and margarine with an electric mixer at low speed until blended. Raise speed to high and continue to beat until light and fluffy, about 5 minutes.
Beat in the ricotta, vanilla, and eggs at medium speed until well blended.
Again reducing speed to low beat in flour, baking powder, and salt until dough forms.
Place level tablespoons of dough, 2 inches apart, onto an ungreased cookie sheet and bake until a light golden color (they will be soft), about 15 minutes.
With a spatula, transfer cookies to a cooling rack; repeat with remaining dough until all dough is baked.
While cookies are cooling, prepare the icing. In a small bowl, mix the confectioners sugar and milk until smooth. With a knife spread icing onto cookies, sprinkle with sprinkles. Let cookies dry completely.