Combine first 5 ingredients in slow cooker.
Add chicken and reserved pineapple juice.
Cover and cook 4 hours on high.
Stir in pineapple tidbits just before serving.
Mix cornstarch and water in a small bowl.
Remove chicken from slow cooker.
Whisk the cornstarch into the sauce in the slow cooker to thicken.
Serve sauce over the chicken.