Still or sparkling?
What it really means
When you ask for water in a restaurant, the waiter may ask this: still (no bubbles) or sparkling (fizzy)? Both are bottled and cost money. If you want free water, ask for "tap water" instead.
Context, tips & common mistakes
"Still or sparkling?" is the waiter's fork in the road after you ask for water — both options mean paid bottled water, and the unlisted third answer is the one locals use: "just tap water is fine, thanks." That answer is fully acceptable in any restaurant, the law backs free water in licensed premises, and no waiter judges you, whatever their eyebrow suggests.
Vocabulary while we are here: sparkling = fizzy = carbonated ('with gas' is understood from visitors but not native phrasing); still means flat. Check the bill afterwards — bottled water occasionally appears despite a tap request, and querying it is routine, not confrontation. If you do want bottled, know it is often priced like a soft drink or worse.