Cocktails with Soda water
Soda water is plain water carbonated under pressure, with no sweetener or flavoring added.
Substitutes for Soda water
The only thing it contributes is gas, so anything carbonated and unsweetened does the same work. Still water is not a substitute at all — it lengthens the drink and leaves it flat — and anything sweetened stops being a neutral lengthener and becomes an ingredient.
Often confused with
Natural sparkling mineral water
Carbonated in the ground rather than at the factory, and it carries its own minerals; in a delicate highball those minerals are tasteable.
Tonic water
Carbonated water with quinine and sugar. The quinine is what makes it bitter and what makes it glow under UV, and it is a flavor ingredient, not a lengthener.
Club soda
Soda water with mineral salts added. Very slightly saline, which some bartenders prefer in a Collins and nobody notices in a long drink.
Storage
Keep it sealed and cold: an open, warm or shaken bottle goes flat and stops doing its job. The point of a small bottle is that opened water cannot be re-carbonated, so buy the volume that will go in one service.
