In France, you have a choice between sweet or savory popcorn while at the movies. "Popcorn Sucré" is sweet popcorn with some "Sucre" (Sugar). It's not Caramel popcorn, it's popcorn tossed with white sugar instead of Salt.
If you're interested in giving some sugar popcorn a try, here is how you can ask for it in French.
Je voudrais du popcorn sucré s'il vous plaît (juh voodray dew popcorn sook ray seal voo play)
Translation: I would like some sweet popcorn please.
This is how you ask for the savory kind with salt.
Je voudrais du popcorn salé s'il vous plaît (juh voodray dew popcorn sal ay seal voo play)
Translation: I would like some popcorn with salt please.
If you're interested in giving some sugar popcorn a try, here is how you can ask for it in French.
Je voudrais du popcorn sucré s'il vous plaît (juh voodray dew popcorn sook ray seal voo play)
Translation: I would like some sweet popcorn please.
This is how you ask for the savory kind with salt.
Je voudrais du popcorn salé s'il vous plaît (juh voodray dew popcorn sal ay seal voo play)
Translation: I would like some popcorn with salt please.