So what am I supposed to call the stuff, anyway? Seltzer? Soda Water? Sparkling Water? Club Soda? Tonic? Our favorite: "Fizzy Water." And is there actually a difference, or are these just different words (regionalisms?) for exactly the same thing?
I am pleased to oblige.
First, there was Water. And it was Good.
Because I stopped listening to science around 6th grade, I believe that you should theoretically be able to make water out of air. I realize that's not true -- it requires some curly-que'd flasks and a thing that goes buzz -- but water you know.
Now gas it up: your water needs more elements in it. It's name is Legion, but I believe there are connotative differences in the term you choose. The origins of the terms themselves are covered in delightful detail on Wikipedia. Pay them or don't pay them; that's their business. We were talking about me.
Seltzer conjures up the art deco spray bottle on the bar that Nick Charles handled so well. Because of that, to me, seltzer is the hard bubbles, the dangerous bottle that has to be opened like cracking a safe. We say it so it rhymes with salsa, and as I have mentioned, Polah makes the craziest Seltzah flavahs evah. It is in fact the same thing as sparkling water. but sparkling water is softer: Pelligrino, for example. Seltzer in the Social Register.
Perrier is too oily, far too soft, and is mineral water anyway. Why accept nature's bubbles when you can trick them out?
"Fizzy Water" is accurate (and charming). It will get you through a language barrier. It could get you served a bromide.
Bromo Seltzer - is your remedy for not having drunk seltzer. It is Tylenol + bicarb + citric acid. And you deserve it. Alka-Seltzer is bicarb + potassium bicarbonate + citric acid, and indistinguishable from Efferdent.
Barley water is what Mary Poppins never smells of. The more you learn about British foods, the more you understand the Revolution.
Club Soda contains added salt. Why? I have no idea. Club Soda is what you say on the airplane, or in any establishment where you know they will not know what seltzer is. It comes out of the gun at the bar. They have it.
Tonic is not club soda. Tonic is the vile mosquito repellent so undrinkable that is requires gin to make it go down. (And they do play nicely together once you introduce them.) Tonic is carbonated water + qunine, and according to Wikipedia, it glows in UV light. You try it; I'm not gonna.