Daft question, but what do you mean by soda water? Do you mean carbonated water or tonic water? Carbonated water (fizzy water) is fine. Tonic water isn't because of the citric acid content. Does your soda water have a list of ingredients on it?
Sparkling water does indeed count as part of your 2.25 litres or 4 pints a day (it doesn't need to be 3 litres unless you're having all tetras/bars). As does the water you add to coffee and tea. As does any extra water you add to your shakes (beyond the recommended amount of water that is).