In large microwavable bowl, measure cereal; set aside. Line cookie sheet with waxed paper or foil.
In 2-cup microwavable measuring cup, microwave butter uncovered on high 30 seconds or until melted. Add granulated sugar and water; microwave uncovered on high 30 seconds or until mixture is heated and can be stirred smooth. Stir in vanilla. Pour over cereal, stirring until evenly coated.
Microwave uncovered on High 4 minutes, stirring every minute, until thoroughly glazed. Sprinkle with powdered sugar; mix well.
Spread on cookie sheet. In small microwavable bowl, microwave white chocolate uncovered on High 30 to 60 seconds, or until it can be stirred smooth. Place in small resealable food-storage plastic bag; cut off small corner of bag. Squeeze bag to drizzle white chocolate over snack mix; sprinkle with edible glitter. Cool until white chocolate is set, about 10 minutes.