PREHEAT oven to 350°F. Line a 13- x 9- x 2-inch pan with Reynolds Parchment Paper, extending paper up sides of pan.
BEAT cake mix, milk, cream cheese, eggs and vanilla in a large bowl on low speed of an electric mixer 30 seconds. Then beat on medium speed 2 minutes, scraping bowl occasionally. Spread batter evenly in parchment-lined pan.
BAKE 35 to 38 minutes or until toothpick inserted in center comes out clean. Cool completely. Invert cake onto a platter; remove parchment paper. Frost cake. Decorate with sprinkles.