HEAT oven to 225ºF.
SPREAD popcorn evenly onto bottom of 15x10x1-inch pan.
BRING sugar, corn syrup and butter to boil in medium saucepan on medium-high heat; cook 3 min., stirring frequently. Remove from heat. Add drink mix and baking soda; mix well. Pour over popcorn; stir gently to evenly coat popcorn.
BAKE 10 min. Remove from oven; stir. Repeat 3 times for a total baking time of 40 min.
SPREAD onto large sheet of waxed paper sprayed with cooking spray; cool completely. Break into pieces.