There are a number of different sugar-free chocolate icing recipes available online, both on cooking websites as well as sugar substitute sites. In many instances, sugar substitutes swap out in even measurements for granulated sugar.
Depending on the type of chocolate, such as semi-sweet chocolate morsels, that is used in the sugar-free frosting recipe, there may be a small amount of sugar present. Recipes that use sugar substitutes tend to be thinner in consistency than those made with granulated sugar, so additions are included into the mix to help thicken the frosting. Typical additions include cornstarch or gelatin. Additional flavor additives can include vanilla extract and chocolate syrup.