Always wondered

Rico says he's been cutting his lemonade with seltzer or, if he doesn't have that, with soda water, and had to look it up:

Club soda and seltzer water are essentially interchangeable. Strictly, seltzer is just water and carbon dioxide (made by pressurizing water with CO2) and club soda may have some other minerals added (like salt). It's more like the difference between Aquafina and Dasani: yeah, there's a difference, but nobody really cares.