Ég drekk kaffi tvisvar á hverjum degi.

Drekka is the infinitive form, like English to drink.

In Icelandic, you have to conjugate the verb for the subject:

• Infinitive: að drekka – to drink
• 1st person singular present: ég drekk – I drink
• 2nd person singular: þú drekkur – you drink
• 3rd person singular: hann/hún/það drekkur – he/she/it drinks
• 1st person plural: við drekkum – we drink
• 2nd person plural: þið drekkið – you (pl.) drink
• 3rd person plural: þeir/þær/þau drekka – they drink

So with ég, you must say drekk, not drekka.

Drekk is the present tense, and in Icelandic the present tense is used both for:

• Right now:
  
  • Ég drekk kaffi núna. – I am drinking coffee now.
• Habitual actions (things you do regularly):
  
  • Ég drekk kaffi tvisvar á hverjum degi. – I drink coffee twice every day.

Because of tvisvar á hverjum degi (twice every day), this sentence clearly refers to a habit, not necessarily this very moment.

In Icelandic, kaffi is usually treated as a mass noun (like English coffee, water, rice), and very often it appears without an article when speaking in general:

• Ég drekk kaffi. – I drink coffee. (in general)
• Ég drekk vatn. – I drink water.

If you want to talk about specific coffee, you use the definite form:

• Ég drekk kaffið. – I am drinking the coffee.
• Ég drekk þetta kaffi. – I drink this coffee.

You normally wouldn’t say something like “a coffee” here in Icelandic; you’d use other constructions (e.g., einn kaffibolla – one cup of coffee).

Kaffi is a neuter noun, and in the singular its nominative and accusative forms are the same: kaffi.

In Ég drekk kaffi, kaffi is the direct object, so it is in the accusative case. But since nominative = accusative for neuter singular here, it looks unchanged.

Very simplified paradigm:

• Nominative singular: kaffi
• Accusative singular: kaffi
• Dative singular: kaffi
• Genitive singular: kaffis

So even though the case changes, the form kaffi stays the same in most everyday uses.

Tvisvar is an adverb meaning twice.

• Ég drekk kaffi tvisvar á hverjum degi. – I drink coffee twice every day.

You can also say:

• tvisvar sinnum – literally twice times
• tveimur sinnum – literally two times (using the dative of tveir = two)

In practice:

• tvisvar = most common, short, natural:
  Ég hef séð hana tvisvar. – I’ve seen her twice.
• tvisvar sinnum = a bit more emphatic / explicit but fine.
• tveimur sinnum = also okay, slightly more “spelled out”.

In your sentence, tvisvar is the most natural and idiomatic choice.

Á hverjum degi literally means “on each day”, and idiomatically “every day”.

• á – a preposition that here has the sense of per / on
• hverjum – dative singular of hver (each, every), agreeing with degi
• degi – dative singular of dagur (day)

The preposition á in this time-expression takes the dative case, which is why you see hverjum degi, not hvern dag.

So the structure is:

• á
  • dative → á hverjum degi (on each day → every day)

It comes from preposition + case rules:

• Á with a time expression like this typically takes the dative.
• The noun dagur (day) in the dative singular is degi.
• The adjective/pronoun hver (each, every) must agree in case, number, and gender with the noun it modifies.

So:

• Nominative: hver dagur
• Accusative: hvern dag
• Dative: hverjum degi
• Genitive: hvers dags

Because á here requires the dative, you get á hverjum degi, not á hvern dag.

Dagur is a masculine noun meaning day. Its singular forms (indefinite) are:

• Nominative: dagur – (subject) Dagurinn er langur. – The day is long.
• Accusative: dag – (direct object) Ég á frí hvern dag. – I have time off every day.
• Dative: degi – (indirect object / after certain prepositions)
  Á hverjum degi drekk ég kaffi. – On every day I drink coffee.
• Genitive: dags – (possession/“of”) í lok dags – at the end of the day.

In á hverjum degi, the form degi is dative singular.

Yes, Ég drekk kaffi tvisvar á dag is also used and understood.

Subtle difference in feel:

• tvisvar á hverjum degi – literally twice on each day; a bit more explicit/emphatic that this is every single day.
• tvisvar á dag – literally twice per day; slightly more compact and general.

In everyday speech, tvisvar á dag is very common. Tvisvar á hverjum degi can sound a touch more formal, careful, or emphatic, but both are correct and natural.

Icelandic word order is fairly flexible, but there are preferences.

Your sentence:

• Ég drekk kaffi tvisvar á hverjum degi.
  Subject – verb – object – time

Other natural variants:

• Ég drekk tvisvar á hverjum degi kaffi. – possible, but much less natural.
• Tvisvar á hverjum degi drekk ég kaffi. – emphasizes the “twice every day” part.

General rule of thumb in neutral statements:

1. Subject
2. Verb (finite verb in 2nd position)
3. Object
4. Adverbs / time expressions / place, etc.

So your original order is the most typical and natural.

The verb drekka is strong and changes its stem in the past.

Present:

• Ég drekk kaffi tvisvar á hverjum degi. – I drink coffee twice every day.

Simple past (habit in the past):

• Ég drakk kaffi tvisvar á hverjum degi. – I drank coffee twice every day.

With other subjects in the present:

• Þú drekkur kaffi tvisvar á hverjum degi. – You drink coffee twice every day.
• Hann/Hún drekkur kaffi tvisvar á hverjum degi. – He/She drinks coffee twice every day.
• Við drekkum kaffi tvisvar á hverjum degi. – We drink coffee twice every day.
• Þeir/Þær/Þau drekka kaffi tvisvar á hverjum degi. – They drink coffee twice every day.

Approximate pronunciation (using an English-friendly guide):

• Ég – [yeh] or [yei], with a slight [ɣ] sound at the end that may be very weak or almost silent.
• drekk – [drekʰ]; the kk is “pre‑aspirated,” like a tiny h before the k.
• kaffi – [kʰafːɪ]; ff is long [fː].
• tvisvar – roughly [tʰvɪs-var]; tv is like “tv” in “TV,” but said together.
• á – [au] (like “ow” in “cow”).
• hverjum – [kʰvɛr-jʏm]; initial hv is like kv.
• degi – [dɛi-jɪ] or [dei-jɪ].

Spoken together at a natural speed:
Ég drekk kaffi tvisvar á hverjum degi. – [yeh drekʰ kʰafːɪ tʰvɪsvar au kʰvɛrjʏm dei-jɪ].