Learn Hardcore Italian: Se hai sete, bevi pure dalla bottiglia: l’acqua è freschissima. - If you are thirsty, feel free to drink from the bottle; the water is very fresh.

Here pure is an adverb meaning “go ahead” or “feel free.” It’s not the same as the English word pure. In bevi pure it softens the command, turning it into a friendly invitation:

Bevi pure! = “Go ahead and drink!”
You see this same usage in phrases like vieni pure (“come on in”) or chiedi pure (“feel free to ask”).

Why is it dalla bottiglia instead of di bottiglia or da una bottiglia?

da expresses origin or source: “from the bottle.”
dalla is the fusion of da + la, because bottiglia is feminine singular.
It’s the definite article (la) because you mean a specific bottle available (the one you’re holding). If you were speaking of any bottle you’d say da una bottiglia (“from a bottle”).

Why is there no article before sete in Se hai sete?

Avere sete is an idiomatic expression: you don’t use an article with these “state of being” nouns. Compare:

avere fame, avere freddo, avere caldo
So you say hai sete (“you’re thirsty”) rather than hai la sete.

What form is bevi, and why isn’t it beve?

Bevi is the tu (second-person singular) form. In the imperative mood (affirmative), bere (to drink) is irregular:

tu bevi (imperative)
Lei beva (formal imperative)
voi bevete
If you used beve, that would be the third-person singular indicative (“he/she drinks”), not an instruction.

Why is it l’acqua instead of la acqua?

Italian elides the article la before a vowel: you drop the a and add an apostrophe. So la acqua → l’acqua. This makes pronunciation smoother.

How is freschissima formed, and what nuance does it carry?

Freschissima is the absolute superlative of fresco (fresh). You form it by attaching -issim- plus the ending matching the gender/number:

fresco → fresch- + ‑issimo → freschissimo (masc. sing.)
fresca → fresch- + ‑issima → freschissima (fem. sing.)
It means “extremely fresh” or “very, very fresh,” stronger than molto fresca.

Why is there a colon (:) before l’acqua è freschissima?

The colon introduces an explanation or result of the first clause. You could also write:

“Se hai sete, bevi pure dalla bottiglia, perché l’acqua è freschissima.”
But the colon is a stylistic choice that tightens the link: “If you’re thirsty, do this: the water is extremely fresh.”

What mood and tense are used in Se hai sete, and why not the subjunctive?

Se hai sete uses the present indicative for a real condition (“if you really are thirsty”). In Italian you don’t use the subjunctive in first (real) conditionals. The pattern is:

Se + present indicative, then main clause (here an imperative).