In a large bowl, cream the butter and sugars until light and fluffy. Beat in egg and vanilla. Combine the flour, drink mix, baking soda and salt; gradually add to creamed mixture and mix well. Stir in malted milk balls. , Shape into 1-1/2-in. balls. Place 2 in. apart on greased baking sheets. Bake at 375° for 10-12 minutes or until set. Cool for 1 minute before removing from pans to wire racks to cool completely.