Learn Hardcore Dutch: Mijn keel is droog, dus ik drink water.

Because droog is a predicate adjective after the verb is. Predicate adjectives in Dutch do not take the -e ending. You do add -e when the adjective comes before the noun (attributive):

Predicate: Mijn keel is droog.
Attributive: Ik heb een droge keel. (common-gender noun → -e)

Can I also say Ik heb een droge keel? Is it more natural?

Yes. Ik heb een droge keel is very common and often sounds more idiomatic in everyday speech. Mijn keel is droog is correct too; it just states a quality more directly. Both are fine.

Why is there no article in ik drink water?

Water is a mass (uncountable) noun, so Dutch normally omits the article in a general sense: ik drink water. Use an article only when it’s specific or countable:

Specific: Ik drink het water (uit die fles).
Some amount: Ik drink wat water.
In cafés you may hear: Ik neem een water (elliptical for “a glass/bottle of water”).

What does dus do to word order? Should it be dus ik drink or dus drink ik?

Dus is a coordinating connector (“so/therefore”). After a comma within one sentence, standard word order is subject–verb: …, dus ik drink water. If you start a new sentence with Dus, it occupies the first position and you invert: Dus drink ik water. You will also hear inversion after a comma (…, dus drink ik …) in modern usage; both occur, but many style guides prefer …, dus ik ….

What’s the difference between dus and daarom?

Both mean “so/therefore,” but they behave differently:

dus is a (coordinating) connector: Mijn keel is droog, dus ik drink water.
daarom is an adverb: if it’s first, you invert: Mijn keel is droog; daarom drink ik water. Nuance: daarom often sounds a touch more explicit/formal as a reason marker.

How do I say “because” instead of “so”?

Use want (coordinating) or omdat (subordinating):

Ik drink water, want mijn keel is droog. (main-clause order)
Ik drink water omdat mijn keel droog is. (omdat sends the verb to the end)

Is the comma before dus required?

It’s optional in Dutch. Many writers insert a comma between two main clauses joined by dus to mark the pause or improve readability, especially if the clauses are longer. Your example with the comma is perfectly fine.

Can I drop the subject and say …, dus drink water?

No. Dutch requires an explicit subject in declarative clauses. Keep ik: …, dus ik drink water. You only drop the subject in imperatives: Drink water!

What’s the gender and plural of keel? Any adjective agreement tips?

Gender: common (de-word) → de keel
Plural: kelen (not “keelen”)
Diminutive: keeltje
Adjective agreement before it: een droge keel, de droge keel (the -e is required because it’s attributive and not neuter-indefinite).

Why isn’t it Mijn keel is droge?

Predicate adjectives (after zijn, worden, etc.) don’t take the -e ending. So it’s droog after is, but droge before the noun: een droge keel.

Is ik ben dorstig a good alternative?

It’s correct but less common in everyday speech. Dutch prefers the “have-thirst” pattern: Ik heb dorst. You can also combine ideas: Ik heb dorst, want mijn keel is droog.

What’s the difference between droog and forms like droogt?

droog = adjective “dry” (as in your sentence).
drogen = verb “to dry.”
droogt = 3rd person singular present of the verb: Het shirt droogt. Don’t use the verb form in your sentence; you need the adjective after is.

How is this pronounced?

Mijn: ij ≈ the vowel in English “eye,” a bit tenser.
keel: ee = long [eː].
is: short [ɪs].
droog: oo = long [oː]; final g is the characteristic Dutch fricative; in the Netherlands often voiceless , in Flanders more voiced [ɣ].
dus: u = [ʏ], like German “ü” but short. Note: r varies by region (rolled, uvular, or lighter).

How is drinken conjugated? Why ik drink and not ik drinken?

Dutch verbs agree with the subject. Present tense of drinken:

ik drink
jij/je u drinkt
hij/zij/het drinkt
wij/jullie/zij drinken So with ik, it’s drink. Past: ik dronk; past participle: gedronken.

Are there other natural ways to say this?

Yes:

Ik heb een droge keel, dus ik drink water.
Mijn keel voelt droog, dus ik drink water.
Intensifier: Mijn keel is kurkdroog, dus ik drink water.