Lemon soda
Lemon soda is a mixer with no alcohol in it, used in 2 drinks on this site.

CC BY-SA 4.0 · Cropped, white-balanced, graded and re-encoded to WebP by eXir.
Clear, carbonated lemon-lime soda in a plain glass
Composition
USDA FoodData Central (SR Legacy) · 173205. Beverages, carbonated, lemon-lime soda, no caffeine. Public domain. Used as the generic figure for both British fizzy lemonade and Spanish gaseosa, which are the same style of drink (carbonated water, sugar and lemon flavouring) under different names. acidPercent left off: no titratable acidity source exists for this specific mixer.
Used in these drinks
most firstSubstitutes
Water: Plain soda water with the lemon dropped; far less sweet and no lemon flavour of its own.
A general substitute is a browsing aid rather than a drink-specific claim. Where a particular drink has a substitution worth making, it says so on its own page and recomputes the spec for it.