Vitamin C is Vitamin Yes in Spanish

Actually, "sie" is pronounced more softly. Like 'zee'

I know, but it was the closest I could get. You don’t have a word like “ssie” or something right? I doubt it because it already looks stupid when I type it

No, but sometimes we do throw in random foreign words. So it'd still kinda be "si" (spanish) then ^^
But I see where you're coming from :)