Cậu tự tráng sạch lọ thủy tinh nhé.

Cậu here means you, but it is not a neutral all-purpose you.

It is commonly used:

• between friends of similar age
• to someone younger in some family/social contexts
• in certain family relationships, where pronouns follow kinship-style rules

For a learner, the safest idea is: cậu is a fairly familiar, casual way to say you.

You should not use it with everyone. For example:

• with a stranger, it may sound too personal or wrong
• with someone older or higher-status, it may be inappropriate

So in this sentence, the speaker is talking in a familiar, not highly formal, way.

Tự means oneself / by oneself / personally.

In this sentence, tự adds the idea that the person should do it themselves:

• Cậu tráng sạch lọ thủy tinh nhé. = Please rinse the glass jar clean.
• Cậu tự tráng sạch lọ thủy tinh nhé. = Please rinse the glass jar clean yourself.

It can imply:

• do it on your own
• don’t wait for someone else to do it
• take care of it personally

So tự adds emphasis to personal responsibility or self-action.

Not exactly.

Tráng usually means to rinse or to swill out, often quickly and usually with water. It often suggests a lighter cleaning action than rửa.

Compare:

• rửa = wash
• tráng = rinse

So:

• rửa bát = wash dishes
• tráng cốc = rinse a cup

In your sentence, tráng sạch means something like rinse it until it’s clean or rinse it clean.

Depending on context, English might translate it as wash or rinse, but the Vietnamese verb itself leans more toward rinse.

Yes, sạch is an adjective meaning clean, but in Vietnamese it often appears after a verb as a result complement.

So tráng sạch means:

• rinse it clean
• rinse it so that it becomes clean

This pattern is very common in Vietnamese:

• lau sạch = wipe clean
• rửa sạch = wash clean
• quét sạch = sweep clean

So sạch is describing the result of the action, not just the object by itself.

Vietnamese often gives requests or commands without a special command marker.

So Cậu tự tráng sạch lọ thủy tinh nhé. is naturally understood as a request/instruction from context and tone.

You could say:

• Cậu hãy tự tráng sạch lọ thủy tinh nhé.

But hãy is often unnecessary in everyday speech, and sometimes it can sound a bit more explicit, deliberate, or instructional.

In casual spoken Vietnamese, leaving out hãy is very normal.

Nhé is a sentence-final particle that softens the request and makes it sound friendlier.

It can add shades like:

• okay?
• please, okay
• all right?
• a gentle reminder

Without nhé, the sentence can sound more direct:

• Cậu tự tráng sạch lọ thủy tinh. = more blunt / plain instruction

With nhé, it becomes softer and more natural in conversation:

• Cậu tự tráng sạch lọ thủy tinh nhé.

This is very common in spoken Vietnamese when making requests.

Lọ thủy tinh means glass jar or glass container, depending on context.

Breakdown:

• lọ = jar, bottle, small container
• thủy tinh = glass

Why not chai? Because chai usually means bottle, especially a narrow-necked one.

So:

• chai thủy tinh = glass bottle
• lọ thủy tinh = glass jar / glass container

The speaker chose lọ because the object is thought of as a jar/container rather than a bottle.

Yes, thủy tinh is a normal and common word for glass as a material.

Examples:

• cốc thủy tinh = glass cup
• bình thủy tinh = glass container
• cửa kính = glass door/window

A useful note:

• thủy tinh is the material
• kính can also mean glass, but often in things like windows, lenses, or eyeglasses

So in lọ thủy tinh, thủy tinh clearly identifies the jar as being made of glass.

Because sạch belongs with the verb as the result of the action.

So:

• tráng sạch lọ thủy tinh = rinse the glass jar clean

Here the structure is basically:

• verb + result word + object

In natural Vietnamese, result expressions like sạch often stay close to the verb:

• rửa sạch tay = wash your hands clean
• lau sạch bàn = wipe the table clean

If you say tráng lọ thủy tinh sạch, it does not sound natural for this meaning. It can sound like the clean glass jar, which changes the structure.

Yes, you could, but the meaning changes slightly.

• tráng sạch lọ thủy tinh = rinse the glass jar clean
• rửa sạch lọ thủy tinh = wash the glass jar clean

Rửa suggests fuller washing. Tráng suggests rinsing, often more lightly or quickly.

Which one is better depends on context:

• if the jar just needs a rinse, tráng is good
• if it is dirty and needs real washing, rửa may be better

So they are close, but not identical.

It is most naturally a gentle request or instruction.

Why?

• cậu makes it personal and direct
• nhé softens it
• there is no harsh particle or strong command word

So it does not sound like a military-style command. It sounds more like:

• Please rinse the glass jar yourself, okay
• You rinse the glass jar yourself, okay

Depending on tone of voice, it could feel:

• friendly
• reminding
• slightly instructive

Sometimes yes, but its position affects what sounds most natural.

In your sentence:

• Cậu tự tráng sạch lọ thủy tinh nhé.

This is very natural. Tự comes before the verb and clearly means do it yourself.

You may also hear similar patterns in other sentences, but for this kind of meaning, subject + tự + verb is the most straightforward and common placement.

So as a learner, this is a good pattern to remember:

• Tôi tự làm. = I’ll do it myself.
• Cậu tự rửa đi. = Wash it yourself.

Not equally.

Lọ is very common, especially in northern Vietnamese. In other regions, people may prefer different words depending on the object, such as:

• chai for bottle
• hũ for jar
• other regional container words

So lọ thủy tinh is perfectly valid Vietnamese, but regional vocabulary may vary.

For learners, the important point is:

• lọ is a container word
• in this sentence it means something like jar

Yes, if the context is clear.

For example:

• Tự tráng sạch lọ thủy tinh nhé.

This can still be understood as a request: Rinse the glass jar yourself, okay.

Vietnamese often drops subjects when they are obvious from context. However, including cậu makes it clearer who the speaker is addressing and gives the sentence a more personal, conversational tone.

So:

• with cậu = clearly directed at that person
• without cậu = still natural if the listener is obvious from context