Use double-sided tape to fasten a festive straw flag about an inch from the top of each straw. Prepare marshmallows for dipping by placing one straw in each. Set out in bowls of sprinkles and sparkling sugar for decorating.
Place white chocolate morsels in a microwave-safe bowl. Microwave morsels on medium power for 15 seconds. Remove bowl and stir the morsels. Return bowl to microwave and continue heating for 15 second intervals, stirring each time until morsels are melted and the chocolate is smooth. Do not overheat!
Dip the marshmallows in the melted white chocolate, then dip or sprinkle in sprinkles and/or sparkling sugar. Place each marshmallow in a cupcake liner.