Buy 4 packs three separate times. The Spend $30 get $10 offer CAN be spread over multiple transactions.
You'll pay $30 and get $10 back, making your out of pocket cost $20, for twelve 12 packs!
That's $1.67 per 12 pack and probably the lowest price you'll find for a while!
Also, if you get 12 packs, you'll have 120 Coke Rewards points, which is almost enough (133) to get one of a few magazine subscriptions they have!