Thumb Score: +23

Amazon [amazon.com] has 6-Pack 16.9-Oz Diet Coke Diet Soda 4 for $21.48 – $6.48 (multibuy discount) – 5% when you check out via Subscribe & Save = $13.92.
Shipping is free with Prime or on $35+ orders.

Savings
Save $6.48 on 4 select item(s) (check and activate [amazon.com])