The 4 multi packs of the 500 ml size. Saw Regular and Zero on offer in my local branch. These sell for at least £1.50 each in those Coke branded vending machines that you see in public places like airports/train stations and shopping centres. Not too sure when offer expires.
Coca Cola 4 x 500 ml pack regular/zero £1.92 @ Sainsburys (may be diet also?)