Personally I always viewed the juice fizzing station as separate from nectar. Like how the juice keg is sims 3 wasn't nectar it was juice. And you could get juiced. And how with the one in sims 4 it's the same thing. And teens have to be "sneaky" when getting it.
I think juice fizzing is literally just various sparkling drinks like sparkling juice, cider, and kombucha. Especially given the pack it came in. And the range of items you can fizz/the resulting products.
Plus if I'm remembering this correctly sims don't get a buzz from those products without a mod. Or at least not the ones I tried. I haven't used it in forever.
Nectar has always been more like wine to me. I didn't get to play with it much (bc both sims 3 bugs and EA saying my packs are missing when they shouldn't be) but I'm fairly sure it's meant to be alcoholic. Idk if there's non-buzzed nectar, but I think it's just the range in various drinks.
Like Juice (capital J) is like beer, fizzed juice is anything sparkling that isn't alcoholic. But myb you could make a hard cider type fizzed juice, if anyone has please lemme know. And nectar is the wines, of sim world. Maybe even other liquors since it's coming in the horse/western pack. I wouldn't be surprised if we got a sim equivalent to whiskey, and things like that in the nectar maker. It's got barrels.