How many ounces is 1 bottle seltzer? Is “seltzer” sparkling water? Club soda?

Hi Jane, a bottle of seltzer is usually 1 liter, or 34 ounces. But you can add as much or as little as you'd like to make it boozier/fizzier to your tastes. As for the difference between seltzer, club soda, and sparkling water, they're all interchangeable in this recipe—they differ in the ways they're carbonated, but not significantly in flavor or fizziness. Just be sure not to use tonic water, which has quinine and sugar added, and has a distinct and bitter taste that might not work so well in this punch. Hope this helps!