Cậu xin nước nữa.

Here, cậu means you.

It is an informal pronoun, usually used for:

• a friend
• a sibling or cousin
• someone of similar age in a close relationship
• sometimes someone younger

It is not a good default choice for strangers, bosses, teachers, or older people.

Vietnamese does not have just one all-purpose word for you.

The pronoun depends on the relationship between the speakers, especially:

• age
• social status
• family role
• level of closeness

So cậu shows a particular kind of informal relationship. In another situation, you might be bạn, anh, chị, em, cháu, and so on.

In this sentence, xin means ask for or request.

It often has a polite or humble feeling, but it does not necessarily mean beg. It is commonly used when asking to receive something or asking permission.

So xin is closer to:

• ask for
• request
• please give me

than to a strong English word like beg.

Because xin and hỏi do different jobs.

• hỏi = ask a question
• xin = ask for something, or ask permission

So if you want information, you use hỏi.
If you want to receive water, you use xin.

Vietnamese does not use articles the way English does.

So nước by itself can mean:

• water
• some water
• the water

The exact meaning comes from context.

Also, because water is a mass noun, Vietnamese does not need a classifier here unless you want to be more specific, such as:

• một cốc nước = a glass of water
• một chai nước = a bottle of water

Yes. Nước has several meanings depending on context, including:

• water
• liquid
• drink
• country or nation

In this sentence, because it comes after xin, it naturally means water or possibly a drink, not country.

Nữa often means:

• more
• again
• another
• additional

In this sentence, it suggests that the action or the amount is not the first one.

Depending on context, English might express it as:

• more water
• water again
• another water/drink

Context decides which nuance is strongest.

Both nữa and thêm can relate to the idea of more.

A simple way to think about them is:

• thêm focuses on adding more
• nữa often means more, again, or another one

In real speech, both are common, and they can even appear together:

• xin thêm nước
• xin thêm nước nữa

So your sentence is fine, but learners should know that thêm is also very common in this kind of situation.

The basic order is:

• Cậu = subject
• xin = verb
• nước = object
• nữa = extra word meaning more/again

So the pattern is basically:

subject + verb + object + nữa

This is normal Vietnamese word order. Vietnamese often puts words like nữa after the thing or action they relate to.

No explicit tense is marked here.

Vietnamese verbs do not change form for past, present, or future the way English verbs do. A sentence like this can be understood from context.

If needed, Vietnamese can add words such as:

• đã for past
• đang for an ongoing action
• sẽ for future

Without those markers, the sentence is tense-neutral.

By itself, without punctuation or extra particles, it is most naturally read as a plain statement.

But in speech, context and intonation matter a lot. Depending on how it is said, it could also sound like an instruction.

If you want to make it more clearly directive, Vietnamese often adds particles such as:

• đi
• nhé
• với

Those make the speaker’s intention clearer.

It is grammatical and understandable, but it sounds fairly plain.

• cậu makes it informal
• xin adds some politeness
• the whole sentence still feels a bit bare on its own

In everyday Vietnamese, speakers often add softening words or use thêm if they want a more natural conversational tone.

So it is fine for learning structure, but in real conversation you may often hear slightly fuller versions.