1In medium bowl, combine chicken, onion pieces, tomato, avocado and eggs; toss gently to mix.
2In small bowl, combine vinegar, oil, sugar, salt, pepper and mustard; mix well. Add to chicken mixture; toss to coat.
3Spoon chicken mixture evenly down center of each tortilla. Top each with spinach and cheese. Fold up bottom edge of each tortilla; fold in sides.