Here in france, everyone says “3w”. Pronouncing it entirely sounds like “Double V, double V, double V” so “3w” sounds like “Trois double V”, which funnily enough, is still longer than world wide web!
But in French “W” is often abbreviated to “V”. Like BMW --> Beh Ehm Veh (often shortened even further to “Beh Ehm”).
So WWW would be “veh veh veh”.
In any case “World Wide Web” is quite the mouthful for the average French speaker.
BMW is a German company. Are you sure that’s not just people saying it in German?