Mặc cả trước, rồi chia tiền cho nước ép không đường.

It is best to learn mặc cả as a fixed expression meaning to bargain / to haggle over a price.

Even though mặc by itself often means to wear, that meaning does not apply here. In this sentence, mặc cả functions as a single verbal idea.

So:

• mặc cả = bargain, haggle

In Vietnamese, words like trước often come after the verb phrase to show sequence.

So:

• mặc cả trước = bargain first
• literally, it is something like haggle first

This is very natural in instructions and short spoken sentences. Vietnamese often says:

• A trước, rồi B = do A first, then B

Here, rồi means then / after that. It links the first action to the next one.

So the structure is:

• Mặc cả trước, rồi...
  = Bargain first, then...

In other contexts, rồi can also mean already, but in this sentence it is clearly the then/next meaning.

Vietnamese often leaves out the subject when it is obvious from context.

This sentence sounds like:

• an instruction
• a reminder
• a suggestion in conversation

So the missing subject is something like you, we, or let’s, depending on context.

That is very normal in Vietnamese. You do not always need to say:

• bạn = you
• chúng ta / mình = we

if everyone already knows who is supposed to do the action.

Literally, chia tiền means divide the money.

In everyday use, it often means:

• split the cost
• split the bill
• each person pays a share

So here it does not usually mean physically separating cash into piles in a mathematical sense. It more naturally means sharing the payment.

Here, cho means for.

So:

• chia tiền cho nước ép không đường
  = split the money for the sugar-free juice

It shows what the money is being split for.

English learners sometimes expect a more direct object pattern, but Vietnamese often uses cho to show purpose or recipient-like relationships. In context, it helps connect the money with the item being paid for.

It is a noun phrase:

• nước ép = juice
• không đường = without sugar / no sugar

So:

• nước ép không đường = sugar-free juice / juice with no sugar

A key pattern in Vietnamese is that the main noun usually comes first, and descriptive information comes after it.

So instead of English-style sugar-free juice, Vietnamese says something closer to:

• juice no sugar

In normal food and drink contexts, không đường usually means without added sugar or unsweetened.

For a drink order, nước ép không đường would usually mean:

• juice with no sugar added

That is the most likely interpretation in real life.

Vietnamese does not use articles like English a and the.

Also, classifiers are not always needed. You usually need one more clearly when you are counting or pointing to a specific unit, for example:

• một ly nước ép không đường = one glass of sugar-free juice
• ly nước ép không đường đó = that glass of sugar-free juice

In your sentence, nước ép không đường is just the item being talked about, so a bare noun phrase is fine.

It is understandable and natural enough in casual speech, especially as a short instruction or note.

It has a slightly compact, spoken feel because Vietnamese often drops anything not strictly necessary.

If you wanted a fuller version, you could say things like:

• Mặc cả trước, rồi chia tiền cho ly nước ép không đường.
• Mặc cả trước, rồi chia tiền mua nước ép không đường.

But the original sentence is perfectly plausible as concise everyday Vietnamese.