Prepare chicken as directed on package. Cut into 1-inch-wide strips. Whisk ketchup, Worcestershire, 1 tablespoon vinegar, soy sauce and garlic powder until smooth.
Toss slaw ingredients with remaining 2 tablespoons vinegar.
Pack each bento box evenly with rice, chicken and slaw. Drizzle chicken with sauce mixture. Refrigerate bento boxes if not consuming immediately.
