1. Coat a 4-quart electric slow cooker with cooking spray. Combine sugar, tapioca, and coconut milk in slow cooker, stirring with a whisk. Cover and cook on LOW for 2 hours or until most of tapioca is transparent. (Pudding will be thin.)
2. Place egg in a medium bowl; stir with a whisk. Add 1/2 cup hot tapioca mixture to egg, stirring constantly with a whisk. Stir egg mixture into remaining tapioca mixture in slow cooker. Cover and cook on LOW for 30 minutes. Turn off slow cooker. Stir pineapple into tapioca mixture; cover and let stand 30 minutes. Serve warm or chilled. Top each serving with toasted coconut.