Efter att barnen hade ätit yoghurt med banan ville de ändå ha en apelsin till.

Because Swedish uses efter att before a full clause with its own subject and verb.

• efter
  • noun phrase: efter maten = after the meal
• efter att
  • clause: efter att barnen hade ätit = after the children had eaten

So here att is needed because barnen hade ätit is a complete clause.

Hade ätit is the past perfect (pluperfect), like English had eaten. It shows that this action happened before another past action.

Timeline here:

1. the children ate yogurt with banana
2. then they wanted an orange too

The other past verb is ville, so hade ätit makes the order very clear.

Barnen means the children. It is the definite plural form of barn.

A quick pattern:

• ett barn = a child
• barnet = the child
• barn = children
• barnen = the children

Swedish often shows definiteness with an ending, not a separate word like English the.

Here yoghurt is being used as an uncountable food noun, similar to English yogurt in They ate yogurt.

So åt yoghurt means they ate some yogurt, not necessarily one specific container.

If you meant one portion or one cup, en yoghurt could also be possible.

In food descriptions, Swedish often leaves out the article when naming an ingredient or flavor.

So:

• yoghurt med banan = yogurt with banana
• glass med choklad = ice cream with chocolate
• te med mjölk = tea with milk

Med en banan would sound more like one actual banana as a separate, countable item.

This is because of the Swedish V2 rule: in a main clause, the finite verb normally comes in the second position.

Basic order:

• De ville ändå ha en apelsin till.

But when the sentence starts with another element, such as Efter att barnen hade ätit yoghurt med banan, that whole part takes the first position. Then the finite verb must come next:

• Efter att ..., ville de ändå ha ...

So ville de is the expected word order here.

Because de is the subject form, like English they, while dem is the object form, like English them.

Here the children are the ones doing the wanting, so they are the subject:

• de ville = they wanted

In spoken Swedish, both are often pronounced dom, but in writing the distinction is usually kept.

Ändå here means something like still, anyway, or all the same.

It adds a contrast:

• even after eating yogurt with banana,
• they still wanted an orange too.

So it emphasizes that the orange was wanted despite what came before.

In a normal main clause, you would say:

• De ville ändå ha en apelsin till.

When another element comes first, Swedish uses inversion:

• Efter att ..., ville de ändå ha ...

So:

• ville = finite verb
• de = subject
• ändå = adverb

That placement is normal Swedish word order.

Because after modal-like verbs such as vilja, Swedish normally uses the infinitive without att.

So you get:

• ville ha
• kunde gå
• måste äta
• ska komma

English uses to here, but Swedish usually does not.

Ha is very common and natural in food contexts. It can mean something like have, but in context it often implies eat or drink.

So:

• ha en apelsin till = have another orange / eat another orange

You could also say äta en apelsin till, but ha sounds very idiomatic in everyday Swedish.

Here till means extra, in addition, or one more.

So:

• en apelsin till = another orange / one more orange

This is a very common Swedish pattern:

• en kaffe till = another coffee
• en gång till = one more time
• två minuter till = two more minutes

En apelsin is indefinite: an orange / one orange.
Apelsinen is definite: the orange.

Here the sentence refers to an additional orange, not one specific orange already identified, so en apelsin is the natural choice.

Also, apelsin is a common-gender noun, so it takes en, not ett.

In Swedish, it is very common not to use a comma between an initial subordinate clause and the main clause.

So this is normal:

• Efter att barnen hade ätit yoghurt med banan ville de ändå ha en apelsin till.

A comma can sometimes appear for style or clarity, but it is often left out in standard Swedish writing.