How do you say soda in Irish Gaelic?

There isn't a single perfect translation for "soda" in Irish Gaelic because the word encompasses different things depending on context. You'd need to be more specific:

* If you mean a carbonated soft drink: The most common translation would be uisce beatha carbónaithe (literally "carbonated living water"). You could also use dí carbónaithe ("carbonated drink").

* If you mean baking soda: The translation is sóid aráin (literally "bread soda").

* If you mean soda water: This would be uisce sóide (soda water).

Therefore, to get the most accurate translation, specify what kind of soda you mean.