Before you get overwhelmed, let’s name the whole family. Tonic water is sweetened with sugar and has bitter quinine—it’s a completely different beast. Sparkling mineral water (like Perrier or San Pellegrino) is naturally carbonated from a spring, with its own unique mineral profile.
Club soda and seltzer are the plain-Jane cousins. But here’s the practical tip: if a recipe calls for “soda water,” use club soda. Most bartenders do. If you’re hydrating, seltzer is better because it’s lower in sodium.
Check the label: a can of club soda can have 50-100 mg of sodium. Seltzer usually has zero. For those watching salt intake, seltzer wins. For a cocktail that needs “depth,” club soda wins.
