I don't know about the Vitamin C part, but these are tasty little suckers, and while they're not Cough Drops, they do help keep your mouth moist and have a little "citrus peel" taste that may be menthol to help soothe the throat a little.
Grapefruit is the best flavor. You have to get the lemon and orange with the grapefruit, but it's worth it. Lemon and orange aren't bad or anything, they're just no grapefruit. Every time you reach in and grab one, you'll be hoping it's grapefruit.