Ek drink eers water en eet dan brood.

Not really. eers ... dan ... is a very common Afrikaans pairing, just like first ... then ... in English.

So:

• eers marks the first action
• dan marks the next action

Using both makes the sequence especially clear and natural.

You can leave one out in some contexts, but the full pair sounds neat and idiomatic:

• Ek drink eers water en eet dan brood. = very clear sequence
• Ek drink eers water en eet brood. = still understandable
• Ek drink water en eet dan brood. = possible, but less balanced

Because Afrikaans often leaves out the subject in the second part of a coordinated sentence when it is the same as the first one.

So these are both possible:

• Ek drink eers water en eet dan brood.
• Ek drink eers water en ek eet dan brood.

The version without the second ek is shorter and very natural.

English usually keeps the subject more often, but Afrikaans can omit it when the meaning is still clear.

Because en is a coordinating conjunction, and the second part is still basically a main clause.

In Afrikaans main-clause word order, the finite verb comes early. Since the subject ek is omitted in the second clause, the verb eet comes first:

• en eet dan brood

If you include the subject, you get:

• en ek eet dan brood

So eet is not being moved to the end. It is staying in normal main-clause position.

This is different from subordinate clauses introduced by words like omdat, where the verb goes later:

• ... omdat ek dan brood eet

Because both nouns are being used in a general, non-specific way.

• water = water in general
• brood = bread in general

This is similar to English:

• I drink water
• I eat bread

You would add an article if you meant something specific:

• Ek drink die water. = I drink the water.
• Ek eet die brood. = I eat the bread.
• Ek eet ’n brood. = I eat a loaf of bread / a bread depending on context, though English normally says a loaf of bread

In this sentence, brood most naturally means bread as a food in general.

So eet brood is like English eat bread.

If you specifically want to talk about one loaf, Afrikaans often uses:

• ’n brood = a loaf of bread

So the bare noun brood is usually the general food item, while ’n brood is more likely one whole loaf.

Because Afrikaans verbs usually do not change according to the subject in the present tense.

So you get:

• ek drink
• jy drink
• hy drink
• ons drink

And likewise:

• ek eet
• sy eet
• hulle eet

This is one of the nice simplifications of Afrikaans compared with English.

Yes, absolutely. That is also correct and very natural.

Afrikaans often moves time words like eers or dan to the front for emphasis:

• Ek drink eers water en eet dan brood.
• Eers drink ek water, dan eet ek brood.

Both are good.

The important thing is that when something comes first in a main clause, the verb still stays in second position:

• Eers drink ek water.
• Dan eet ek brood.

That is why Eers ek drink water is wrong.

No. eers can also mean something like only, not until, or only later, depending on context.

For example:

• Ek kom eers môre. = I’m only coming tomorrow / I’m not coming until tomorrow.

But in your sentence, because it is paired with dan, the meaning is clearly first:

• eers ... dan ... = first ... then ...

So here there is no ambiguity.

Yes. That is also correct.

Compare:

• Ek drink eers water en eet dan brood.
• Ek drink eers water en dan eet ek brood.

The difference is mostly style and rhythm.

• en eet dan brood is a bit tighter and more compact because the second ek is omitted
• en dan eet ek brood sounds slightly fuller and gives a bit more emphasis to then

Both are natural Afrikaans.