Tests reveal that more than half of leading soft drinks, like Coke and Pepsi, contain traces of alcohol, according to French research.
Only cheap supermarket versions of the drink are alcohol-free.
French magazine 60 Million Consumers published results of tests on 19 kinds of colas.
The results suggest that the alcohol levels are as low as 10mg in every litre, or around 0.001 per cent alcohol.
Only nine that did not contain alcohol were made by brands including Auchan, Cora, Casino, Leader Price and Man U-Cola. The ten which had traces of alcohol included Coca-Cola, Pepsi Cola, Coca-Cola Classic Light and Coke Zero.
Coca-Cola Franch acknowledged that "it is possible that traces of alcohol come from the process" of making Coca Cola according to its secret recipe.
Pepsi, meanwhile, said "some soft drinks can contain minute traces of alcohol because of the ingredients used", but denied that its recipe contains alcohol.
Both companies suggested that natural fruit can ferment and produce minute traces of alcohol.