Sparkling water is still water that has been carbonated with dissolved CO₂ under pressure. Naturally sparkling mineral water contains minerals (calcium, magnesium, bicarbonate) from its source; artificially carbonated water is nutritionally identical to still water unless minerals are added. Carbonation does not meaningfully affect tooth enamel at the low acidity of plain sparkling water, though flavoured varieties are more acidic.
An excellent calorie-free alternative to sugary soft drinks; the carbonation provides a more satisfying, filling sensation than still water for some people. Flavoured sparkling waters (check labels) may have added acids that are more erosive.