I don't know for other European countries, but at least I can say that it is not true in France. "Coke" is reserved for cocaine, and cola is the generic word for Coca-Cola-like beverages.
"Charbon". The French commoner will refer to the rock coke as "charbon de terre", shortened to charbon. Similar to "pomme" is apple, and "pomme de terre" is apple from the earth (potato). Charbon is also the word for charcoal.
So my grandma used charbon (coke) when she was a kid. And my mom uses charbon (charcoal) for her barbecue.
In journals and scientific papers the words coke will be used.
In everyday speech, coke means cocaine. Coca is short form for coca cola. And cola is the generic for a coca cola flavored soda.
In everyday speech, coke means cocaine. Coca is short form for coca cola. And cola is the generic for a coca cola flavored soda.
I admittedly used a very rare/specialist example homonym. What I'm really wondering is how context plays into it. If you're ordering drinks in France and an English speaker says they'll have a Coke, does anyone really think they are referring to cocaine? Coke is vernacular slang for cocaine in American English too, but no one confuses this with usage of the brand name to refer to soft drinks (specifically Coca-Cola, or to soft drinks in general, which is a regional thing).
"Un coke s'il vous plaît" is not a proper French sentence. It does not sound right. It will be obvious it's a language difference and people will easily guess coca cola. In fact French people will most likely quip back "Un coca vous voulez dire ?".
Fun aside, coca cola/cola is male. Cocaïne is female. A rail (of coke) is male.
If you say the word coke (\kok\) in front of a Frenchman, they will immediately think of cocaine. Most people aren't aware of the other meaning of coke. They will probably say it's coal (charbon), the technical term being coke (but pronounced \kɔk\) or apparently charbon de terre according to the other comments.
In France coca is a bit generic term for coca cola and pepsi
But if you have a brand that sell coke we use cola
Like breizh cola or a <supermarket brand> cola