Reader Lori found a great deal on the Slim-Fast Optima Ready to Drink Shakes at Amazon. They are on sale for $19.92 (org $39.99). Plus you can get 15% off when you choose Subscribe & Save and then an additional 15% off with coupon code SLIM2OII. So only $13.94 for the case or $0.58 per can. Plus it ships free with Amazon Prime.
When you get your shipping notification, you can log into your Amazon account and update your Subscribe & Save so you do not continue to receive shipments.
(Thanks Lori!)