You'd save up a few ha'pennies in an old margarine tub and swap them for a bottle of flat coke. One of your mates would then have to put the bubbles in, using whatever gas was to hand. The good old days.
Who in their right mind would let a bottle of coke go flat, surely it was more fun to drink said coke (when fizzy) and then belch out swear words.
Pete
Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in