So, is there a difference? Yes, and it’s mostly chemical and psychological. If you ask for a seltzer and get a soda water, you might feel cheated. If you ask for a soda water and get a seltzer, you might feel... clean? But either way, you’re not wrong. You’re just thirsty.
Here’s my final, completely unsolicited advice: use seltzer for drinking straight, for being a boring hero at a party, or for making your kids’ juice boxes look fancy. Use soda water for cocktails, because you want that mineral backbone. And if someone offers you club soda, just nod and smile. It’s soda water with a PhD in edge.
Now go forth. Be bubbly. And if anyone tries to correct you? Tell them you’re a connoisseur of effervescence. They’ll be too confused to argue.
