Learn Hardcore Spanish (Spain): Es mejor no quedarse sin agua en la montaña. - It is better not to run out of water on the mountain.

Quedarse sin + noun is the most common, everyday way to say “to run out of / end up without.” It often highlights that the subject is affected by the loss: Nos quedamos sin agua.
Quedar sin + noun also exists, especially with inanimate subjects or in a more formal/newsy style: Varios barrios quedaron sin agua. If in doubt, use quedarse sin, which is always natural in this meaning.

Could I say estar sin agua instead of quedarse sin agua?

They’re different:

Estar sin agua = to be without water (a state): Estamos sin agua (we don’t have water).
Quedarse sin agua = to run out of water (a change/result): Nos quedamos sin agua (we used it up / it’s gone). In your sentence, the idea is “don’t end up running out,” so quedarse sin fits best.

Where does no go with an infinitive and a reflexive verb? Why no quedarse and not no se quedar?

With an infinitive, the negative no comes right before the infinitive, and the reflexive pronoun stays attached to it:

Correct: no quedarse
Incorrect: no se quedar If you personalize it, you attach the pronoun that matches the subject: no quedarte, no quedarse, no quedarse, no quedarnos, etc. With a conjugated form, the pronoun goes before the verb: no te quedes.

Why use Es mejor + infinitive instead of Es mejor que + subjunctive?

Both are correct; they differ in focus:

Es mejor no quedarse sin agua… = a general recommendation (impersonal).
Es mejor que no te quedes sin agua… = directed at a specific person or group and requires the subjunctive (te quedes, os quedéis, etc.). Meaning is essentially the same; choose based on how personal you want it to sound.

Can I drop es and say Mejor no quedarse sin agua…?

Yes. In Spain, Mejor… at the start of a sentence is a very common, slightly more informal way to say Es mejor…. Example: Mejor no te quedes sin agua en la montaña.

Is no redundant with sin here? Isn’t that a double negative?

No. No negates the verb (quedarse), while sin is a preposition meaning “without.” They don’t cancel each other out. The structure is normal: no quedarse sin X = “not end up without X.”

Why en la montaña and not en las montañas?

In Spain, en la montaña often means “in the mountains/mountain environment” in a generic sense. En las montañas is also possible, but it tends to emphasize multiple mountains or specific ranges. All of these can be natural, depending on nuance:

Generic environment: en la montaña
Specific ranges or multiple mountains: en las montañas
A mountain range: en la sierra
Countryside/wooded hills: en el monte

Why does Spanish use the article in en la montaña? Could I say en montaña?

Spanish generally uses an article with singular countable nouns, even when speaking generically. En la montaña is the natural phrasing. En montaña is not idiomatic in this meaning.

Shouldn’t it be el agua? Why is it sin agua?

The noun agua is feminine, but takes el with the singular definite article to avoid the clash of sounds: el agua fría, esta agua. The adjective stays feminine: fría.
After sin, you usually don’t use an article when speaking generally: sin agua = “without water (in general).”
Use sin el agua only if you mean a specific water supply: sin el agua del bidón.

Why singular agua and not plural aguas?

Here agua is a mass noun (like “water” in English), so it’s singular: sin agua. The plural aguas is used for types or bodies of water: las aguas termales, las aguas del río.

Are there other natural ways to express “run out of water”?

Yes:

quedarse sin agua (most common): Nos quedamos sin agua.
acabársele el agua a alguien: Se me acabó el agua.
terminársele el agua a alguien: Se te terminó el agua. For advice: Asegúrate de que no se te acabe el agua / Procura no quedarte sin agua.

Is Es mejor no te quedes sin agua… correct?

No. Combine them like this:

Impersonal + infinitive: Es mejor no quedarse sin agua…
Personal + subjunctive: Es mejor que no te quedes sin agua…
Colloquial without es: Mejor no te quedes sin agua…

Why es and not está in Es mejor?

Use ser (es) for general evaluations and inherent qualities: Es mejor/peor/aconsejable…. Estar (está) would suggest a temporary or comparative state of something specific, not a general recommendation.

Who is the subject of quedarse in this sentence? There’s no person mentioned.

It’s an impersonal, general statement. Es mejor no quedarse… means “It’s better not to run out…” in general (think “one/you/people”). If you want to aim it at someone, specify the pronoun: Es mejor que no te quedes… / Mejor no os quedéis…

What’s the difference between quedar and quedarse in general?

Quedar (non‑reflexive) has several meanings: to remain, to be left, to fit/suit, to arrange to meet. Examples:
- Me queda agua. (I have some water left.)
- ¿Quedamos a las seis? (Shall we meet at six?)
Quedarse (reflexive) often means to stay, end up, or be left without:
- Me quedé en casa.
- Nos quedamos sin agua. In the “run out of” sense, use quedarse sin.