A bargain? - I don't think so!

I had to fill my car with petrol this morning. Whilst the paying the cashier casually asked me if I'd like to by 2 bottles of Coke for £2. I automatically said no, but looked at the display the cashier had gestured towards... The bottles of Coke were the 500ml size! I just had to tell the cashier that you could get 3 bottles of Pepsi the same size for a £1 in Farmfoods! (Or Nettos?) These garages really take the p*$! with there so called offers...