[bombela]

"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.

[thwarted]

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).

[bombela]

"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.