Learn Farsi: این نوشیدنی گوارا باد.

bâd is a historical form of the verb 'to be' used specifically in the optative mood to express wishes, blessings, or prayers. While you could use the regular subjunctive bâshad, bâd acts as a fixed, poetic expression for 'may it be.'

If the subject were plural, like 'these drinks', would bâd take a plural ending?

No, it remains exactly the same. In modern Farsi, bâd and its negative form mabâd are invariant. They act almost like set particles of wishing at the end of a sentence and do not conjugate for person or number.

How is the noun nushidani constructed from the verb 'to drink'?

It is formed by taking the full infinitive nushidan (to drink) and adding the suffix -i. This creates a noun or adjective meaning 'something to be drunk' or 'beverage'. You will recognize this pattern from other words you know, like khordani for food or didani for attractions.

Does gavârâ refer to anything refreshing, like a cool breeze?

No, gavârâ specifically means refreshing, palatable, or pleasant to swallow, and it is almost exclusively paired with drinks like water or tea. It is closely related to the polite phrase gavârâ-ye vojud, which you say to someone after they have had a drink.