The guideline daily amounts given on a bottle of Tesco cola are calculated on the basis of 100ml. A typical serving is normally regarded as a 330ml can.
In the above example you can probably justify it, though. If all nutritional information is given in 100ml, and it is on the half litre bottle of Coke in front of me, then Tesco would be shooting themselves in foot by show information about 3 times that amount. People are only looking at the relative healthiness of a product rather that any kind of absolute. Plus, you know, if you're looking at the wholesomeness of a bottle of Coke chances are you're just not eating right anyway.
It's kind of like the standard stand-up thing about "meals for two" actually being equivalent to a single portion just because you don't want the checkout person (who really couldn't care less and I should know I did my bit for Tescos when I was at college) to know that you'll be eating home alone tonight.