Just went into Asda Gosforth and saw this deal. Online as well.
2 share size Cokes (1.25Litre bottles) for £1.50, usually £1.37 each.
The standard 2L bottle is £1.66, or 3 for £4 - £1.50 per litre.
This is 60 pence per litre.
Looks like a good deal to me...!