I checked the phrase, and it seems to be a promotion for a bar. Perhaps it should read "sparkling wine"? That would be champagne. Officially, if sparkling wine is not produced in the Champagne region (northeast France), then it shouldn't be called "champagne". "Free flow sparkling wine" means champagne poured out - perhaps it's free champagne? If it's not an error and it really means "line", that would still refer to a range of alcoholic (sparkling) drinks from the same producer.

Not entirely sure what the context is.. but it seems to be saying that the sparkling line is by no means just a straight line but goes in its own path. Makes the line not seem just straight and instead flowing freely just like a river doesn't go down a straight path and bends and travels. So does this sparkling line.