Dip pretzel rods. Melt birthday cake Candy Melts candy according to package directions. Dip pretzel rods halfway in melted candy. Tap to smooth and remove excess candy. Place on parchment-covered cake boards. Immediately sprinkle with rainbow nonpareils. Chill until firm, about 10 to 15 minutes.
Drizzle remaining pretzel rods. Place pretzel rods on parchment-covered cake board. Use melted candy in cut parchment bag to drizzle over pretzel rods. Chill until firm, about 3 to 5 minutes.