Watoto walikula sandwichi mbili zenye jibini, halafu wakanywa maziwa.

It has three main parts:

• wa- = they
• -li- = past tense
• -kula = eat

So walikula means they ate.

In this sentence, wa- matches watoto (children).

Because Swahili verbs usually agree with their subject.

Here, the subject is watoto (children), which is a plural human noun. Plural human subjects normally take the subject prefix wa-.

So:

• watoto walikula = the children ate
• watoto wakanywa = the children then drank

Even when the noun watoto is stated explicitly, the verb still keeps its subject prefix.

Sandwichi is a loanword, and many Swahili loanwords do not change form between singular and plural.

So you can have:

• sandwichi moja = one sandwich
• sandwichi mbili = two sandwiches

The number is shown by context, numerals, and agreement words rather than by changing the noun itself.

In Swahili, numbers usually come after the noun they describe.

So:

• sandwichi mbili = two sandwiches
• watoto wawili = two children

This is normal Swahili word order. English says two sandwiches, but Swahili says sandwiches two.

Zenye comes from -enye, which means something like having, with, or that have.

So:

• sandwichi mbili zenye jibini = two sandwiches with cheese
• more literally: two sandwiches that have cheese

The form zenye is used because sandwichi here is plural.

Compare:

• sandwichi yenye jibini = a sandwich with cheese
• sandwichi zenye jibini = sandwiches with cheese

Because -enye changes to agree with the noun class of the noun it describes.

Here, sandwichi is being treated as a plural noun, so the agreeing form is zenye.

A learner does not need every agreement pattern at once, but the important idea is:

• Swahili often makes describing words agree with the noun
• zenye is the correct agreeing form here for plural sandwichi

So sandwichi mbili zenye jibini is grammatically matched.

Yes, that would also be understandable and natural in many contexts.

There is a slight nuance:

• zenye jibini = with cheese / containing cheese
• za jibini = of cheese / cheese sandwiches

In everyday speech, the difference is often small. In this sentence, zenye jibini emphasizes that the sandwiches had cheese in them or on them.

Because Swahili usually does not use articles like the or a/an.

So:

• watoto can mean children or the children, depending on context
• maziwa can mean milk or the milk, depending on context

The listener figures it out from the situation, not from a separate article word.

Halafu means then, after that, or and then.

It connects the first action to the next one:

• Watoto walikula ... = The children ate ...
• halafu wakanywa maziwa = then they drank milk

So it helps show the order of events.

This is a very common learner question.

Wakanywa contains -ka-, which is often used for the next action in a sequence. It gives a sense like and then or next.

So:

• walikula = they ate
• wakanywa = then they drank

This is very natural in narration.

You could also say halafu walikunywa maziwa, and that would still make sense. But wakanywa sounds more like a continuing sequence of events in a story.

Also note that the verb stem comes from kunywa (to drink), so:

• wa-ka-nywa = they then drank

Because Swahili finite verbs normally include a subject marker.

So even though watoto is already stated, the verb still shows who did the action:

• wa-likula = they ate
• wa-kanywa = they then drank

This is normal Swahili grammar. The noun and the verb agreement often appear together.

Maziwa is the normal Swahili word for milk, even though its form belongs to a class that often looks plural.

For learners, the safest thing is simply to memorize:

• maziwa = milk

It does not usually mean milks in the English sense here. It is treated as a mass noun.

Also, be careful: ziwa by itself usually means lake, not one milk.

The sentence follows a very common Swahili pattern:

• Watoto = subject
• walikula = verb
• sandwichi mbili zenye jibini = object + its modifiers
• halafu = connector
• wakanywa = next verb
• maziwa = object

So the structure is roughly:

Subject + verb + object, then connector + verb + object

One important difference from English is that modifiers such as numbers and descriptive phrases usually come after the noun:

• sandwichi mbili
• sandwichi zenye jibini