Jeg drikker ikke kaffe, og min søster drikker heller ikke kaffe.

In a normal Danish main clause, the finite verb usually comes early, and ikke normally comes after that verb.

So the pattern is often:

• subject + verb + ikke + object

That gives:

• Jeg drikker ikke kaffe

English uses do in a sentence like I do not drink coffee, but Danish does not need an extra helping verb here.

A useful comparison:

• Main clause: Jeg drikker ikke kaffe
• Subordinate clause: ... fordi jeg ikke drikker kaffe

In subordinate clauses, ikke usually comes before the verb.

Heller ikke means not either or neither.

So:

• min søster drikker heller ikke kaffe

means:

• my sister does not drink coffee either

It connects the second negative statement to the first one.

Compare:

• Jeg drikker ikke kaffe. = I do not drink coffee.
• Min søster drikker heller ikke kaffe. = My sister does not drink coffee either.

A very important point: the standard expression is heller ikke, not ikke heller.

Because this is a main clause, and in Danish main clauses the finite verb usually comes in second position.

So the normal order is:

• min søster = subject
• drikker = finite verb
• heller ikke = adverbial
• kaffe = object

That gives:

• Min søster drikker heller ikke kaffe

If you put heller ikke before drikker, it sounds wrong in a normal main clause.

But in a subordinate clause, that kind of order can happen:

• ..., at min søster heller ikke drikker kaffe

So the difference is really about main clause vs. subordinate clause word order.

Because søster is a common-gender noun in Danish.

You can tell because the indefinite form is:

• en søster

With en-words, you use:

• min = my

With et-words, you use:

• mit = my

So:

• en søster → min søster
• et hus → mit hus

And in the plural, Danish uses:

• mine

for both genders.

Because kaffe is being used in a general sense, like a substance or category, not as a coffee or the coffee.

So:

• Jeg drikker ikke kaffe = I do not drink coffee

This is the same idea as English, where we often say I drink coffee without an article.

If you say:

• en kaffe

that usually means a coffee, often understood as a cup of coffee.

So these are different:

• Jeg drikker ikke kaffe = I do not drink coffee, generally
• Jeg drikker ikke en kaffe = I am not drinking a coffee / a cup of coffee

Because Danish verbs usually do not change according to the subject the way English verbs sometimes do.

In the present tense, Danish uses the same verb form for all persons:

• jeg drikker
• du drikker
• han drikker
• vi drikker
• de drikker

So there is no special form like English drinks for he/she.

That is why both parts of the sentence use:

• drikker

Drikker is the present tense of drikke.

In this sentence, the present tense is used for a habit or general fact, not just for something happening right now.

So:

• Jeg drikker ikke kaffe

means something like:

• I do not drink coffee
• I am not a coffee drinker

It is not limited to this exact moment.

Not in the sentence exactly as it stands, unless the context is very clear. If you simply say:

• Jeg drikker ikke kaffe, og min søster drikker heller ikke

it may sound incomplete, because drikker usually needs something after it here.

A more natural shorter version is:

• Jeg drikker ikke kaffe, og det gør min søster heller ikke

That means:

• I do not drink coffee, and neither does my sister

So yes, you can avoid repeating kaffe, but you usually change the structure when you do.

Yes, you can, but it is not exactly the same in feel.

• Jeg drikker ikke kaffe is the most natural general statement for I do not drink coffee
• Jeg drikker ingen kaffe puts more focus on no coffee / not any coffee

So ingen is more about the absence of any amount, while ikke is the normal way to negate the whole statement.

For a general habit, Jeg drikker ikke kaffe is usually the best choice.

Og means and and joins the two clauses together:

• Jeg drikker ikke kaffe
• min søster drikker heller ikke kaffe

Both clauses are complete on their own, and og simply links them.

So the sentence is built as:

• I do not drink coffee, and my sister does not drink coffee either

This is a very common way to connect two related statements in Danish.