Learn Hardcore Dutch: Ik eet liever jam op mijn boterham en drink er yoghurt bij. - I prefer to eat jam on my slice of bread and drink yogurt with it.

Ik heb liever jam dan honing.
= I prefer jam to honey. (preference between two foods)
Ik eet liever jam.
= I prefer to eat jam. (preference between actions/choices of what to eat)

In your sentence, Ik eet liever jam op mijn boterham focuses on what you prefer to do (eat jam on your bread).

Why is it Ik eet liever jam and not Ik liever eet jam or Ik eet jam liever?

Dutch main clauses are verb-second: the finite verb (here eet) must be in the second position. That already fixes Ik eet at the start.

Adverbs like liever usually come after the finite verb:

Ik eet liever jam. ✅ natural
Ik liever eet jam. ❌ wrong word order (finite verb not in second position)
Ik eet jam liever. ⚠️ grammatically possible, but sounds less natural and adds a bit of emphasis on jam (“I eat jam rather, not something else”).

So the neutral, normal word order is:

Ik (subject)
eet (finite verb, position 2)
liever (adverb)
jam op mijn boterham (rest of the sentence).

Why is there no article before jam and yoghurt (no de/het or een)?

Jam and yoghurt are used here as mass nouns (uncountable), referring to some amount of those substances in general, not a specific portion.

In English you also say:

“I eat jam on my toast” (not a jam),
“I drink yoghurt” (not a yoghurt, unless you mean a yoghurt drink container).

Similarly in Dutch:

Ik eet jam. = I eat jam.
Ik drink yoghurt. = I drink yoghurt.

You would add an article when you talk about a specific portion or product:

Ik eet een yoghurt.
= I eat a yoghurt (one yoghurt dessert, a pot/cup).
Ik drink een yoghurtje.
= I drink a little yoghurt drink.

But in your sentence the speaker is talking about what they generally consume with their bread, so no article is needed.

What exactly is a boterham? Is it just “bread,” or is it “sandwich”?

A boterham is roughly:

a slice (or two slices) of bread prepared as something you eat, usually with a topping.

Important nuances:

It’s not “bread” in general (that’s brood).
It often corresponds to “a (simple) sandwich” in English, especially at breakfast/lunch:
- Ik eet drie boterhammen.
  = I eat three sandwiches / three slices of bread with toppings.

Culturally:

In Dutch-speaking countries, a typical breakfast or lunch is several boterhammen with cheese, jam, etc.
A big, elaborate sandwich with lots of fillings is more likely called een broodje or een sandwich.

So jam op mijn boterham is like “jam on my slice of bread / on my sandwich.”

Why is it op mijn boterham and not met jam or op mijn brood?

All are possible, but they’re not identical in nuance:

op mijn boterham
Literally “on my slice of bread.” This emphasizes the slice-as-a-meal (the prepared piece you eat).
met jam
Means “with jam.” It focuses on jam as the accompaniment:
- Ik eet mijn boterham met jam.
  = I eat my sandwich with jam on it.
op mijn brood
Brood is “bread” in general (the product or the loaf), so:
- Ik eet liever jam op mijn brood. is grammatically okay, but less idiomatic if you mean a specific slice you’re eating now.
- In everyday speech, op mijn boterham sounds more natural for “on my slice of bread / on my sandwich.”

In the given sentence, op mijn boterham is the standard, most idiomatic way to say this.

Why is there no ik in the second part: … en drink er yoghurt bij instead of … en ik drink er yoghurt bij?

Dutch often omits the subject ik in a coordinated clause when:

It’s the same subject as in the previous clause, and
The clauses are closely connected with en (and), maar (but), etc.

So these are both correct:

Ik eet liever jam op mijn boterham en drink er yoghurt bij.
Ik eet liever jam op mijn boterham en ik drink er yoghurt bij.

The version without ik in the second clause sounds more fluent and natural in everyday speech. Adding ik makes the structure a bit heavier or more emphatic (for example, if you contrast it with what someone else drinks).

What does er mean in drink er yoghurt bij? What is it referring to?

In drink er yoghurt bij, er is a little pronoun that roughly stands for “with it / with that.”

Here, er refers back to the situation just mentioned: eating a boterham with jam. So the idea is:

Ik eet liever jam op mijn boterham
= I prefer to eat jam on my sandwich
en drink er yoghurt bij.
= and I drink yoghurt with that (meal).

So er … bij together functions like “with it”:

Ik drink er yoghurt bij.
≈ I drink yoghurt with it.

Dutch uses er a lot as a placeholder pronoun like this, and it’s very common with short adverbs/prepositions like erbij, eraan, erover, etc.

Why is it er yoghurt bij and not yoghurt erbij or erbij yoghurt?

Several word orders are possible, but they have different statuses and nuances.

In Ik drink er yoghurt bij:

er is an unstressed pronoun and likes to stand early in the clause (in the so‑called “middle field”).
yoghurt is the direct object.
bij is the small adverb/preposition that completes er … bij (“with it”).

So you get:

Ik (subject)
drink (finite verb)
er (pronoun referring to the situation/meal)
yoghurt (object)
bij (adverb/preposition, forming er … bij)

Other variants:

Ik drink yoghurt erbij.
= Also correct. Now erbij stays together at the end. This may sound a bit more like you’re adding something extra (“I drink yoghurt on top of that”).
Ik drink erbij yoghurt.
= This is unusual and sounds wrong in standard Dutch.

So Ik drink er yoghurt bij is very natural and common, with the unstressed er placed before the main object.

Could I just say Ik drink liever yoghurt bij mijn boterham? How is that different from Ik drink er yoghurt bij?

Yes, you can say:

Ik drink liever yoghurt bij mijn boterham.
= I’d rather drink yoghurt with my sandwich.

Differences:

liever vs no liever
- Ik drink er yoghurt bij.
  = I (typically) drink yoghurt with it. A simple statement of habit, no explicit comparison.
- Ik drink liever yoghurt bij mijn boterham.
  = I would prefer to drink yoghurt with my sandwich (maybe instead of coffee, milk, etc.).
er vs explicit phrase
- er in Ik drink er yoghurt bij is referring back to the previously mentioned meal without repeating bij mijn boterham.
- In bij mijn boterham, you say explicitly “with my sandwich.”

So:

Ik drink er yoghurt bij.
= I (usually) drink yoghurt with that (meal/bread).
Ik drink liever yoghurt bij mijn boterham.
= My preferred drink with my sandwich is yoghurt.

Does Ik eet liever jam op mijn boterham mean “I’m eating jam right now” or “I generally prefer jam on my bread”?

In Dutch, the simple present often covers both:

A general preference / habit:
- Ik eet liever jam op mijn boterham.
  = As a rule, I prefer jam on my bread (rather than something else).
A current situation or choice:
- In the right context (e.g. at the table choosing between jam and cheese):
  Ik eet liever jam op mijn boterham.
  = Right now, I’d rather have jam on my bread.

Dutch uses the continuous form (ik ben aan het eten) much less than English; the simple present is usually enough. In your sentence, without any extra context, English speakers will usually interpret it as a general preference.