Line tray or baking sheet with wax paper. Insert 1 stick into stem end of each apple.
Microwave caramels and water in large, microwave-safe bowl on HIGH (100%) power for 2 minutes; stir. Microwave at additional 10- to 20-second intervals, stirring until smooth.
Dip each apple in melted caramel; scrape excess caramel from bottoms. Quickly roll bottom half of apples in chopped Butterfinger, then place on prepared tray. Refrigerate for 45 minutes or until set. Store apples in refrigerator in airtight container. Apples are best if they are served the same day as they are prepared.