Heat the apricot jam and water (if using) in a small saucepan over medium heat until liquid (melted). Remove from heat and strain the jam through a fine strainer to remove any fruit lumps. (If using, add the liqueur at this point.) Let cool until it is only slightly warm and then glaze the fruit or tart crust, using a pastry brush. Note: only lightly coat the fruit or tart shell with the glaze so that it does not look jelly-like when dry.