Learn Hardcore Russian: Мне вредно пить газировку каждый день. - It is harmful for me to drink soda every day.

Russian uses the dative case to mark the “experiencer” in impersonal sentences with predicatives like вредно, можно, нужно, полезно, холодно. So you say кому? — мне (to whom? — to me). The literal structure is “To me it is harmful to drink soda every day.”
Common patterns: Мне холодно, Мне нужно учиться, Мне можно/нельзя есть орехи, Мне полезно гулять.

What exactly is вредно here: an adverb or an adjective?

It’s a predicative (short-form adjective in neuter), often taught as a “category of state” word. In this impersonal use, вредно doesn’t agree with any noun; it’s a fixed predicate meaning “harmful.” Compare with short forms when there is an explicit subject: вреден (m), вредна (f), вредно (n), вредны (pl).

Why is пить in the infinitive?

The infinitive can function as the subject-like element of an impersonal sentence: “To drink soda every day is harmful (to me).” So пить names the general activity that is evaluated as harmful.

Why is газировку in the accusative?

Because it’s the direct object of пить. The verb “to drink” takes its object in the accusative: пить воду/чай/кофе/газировку. Nominative: газировка; accusative: газировку.

Can I say Мне нельзя пить газировку каждый день instead? What’s the difference from вредно?

Мне вредно… = “It’s harmful for me (bad for my health).”
Мне нельзя… = “I must not / I’m not allowed / I shouldn’t (forbidden or contraindicated).”
Often a doctor’s advice can be phrased either way, but нельзя emphasizes prohibition/contraindication, while вредно emphasizes harm.

Is the word order fixed?

No. Russian word order is flexible; changes affect emphasis, not basic meaning. All are correct:

Мне вредно пить газировку каждый день (neutral).
Пить газировку каждый день мне вредно (emphasis on “for me”).
Мне вредно каждый день пить газировку (focus on the frequency).
Каждый день пить газировку мне вредно (fronts the frequency/adverbial).

Which verb should I use for habits: пить, выпивать, выпить, попить?

пить: generic, habitual process. Best default here.
выпивать: “to (tend to) drink up,” often about regular consumption or amounts (e.g., выпивать по банке в день).
выпить: single completed act (“to drink (up) once”).
попить: to drink for a while / some.
With каждый день, use пить or выпивать.

Can I omit мне for a general statement?

Yes: Пить газировку каждый день вредно. That states a general truth. Adding мне personalizes it: it’s harmful specifically for me.

How would I say it with an explicit subject like “Soda is harmful to me”?

You can say Газировка вредна мне or Газировка вредна для меня. More commonly, Russians say Газировка вредна для здоровья (“Soda is harmful to health”). The impersonal pattern with an infinitive (Мне вредно пить…) is the most natural when evaluating an activity.

How do I say this for other people (you, him, them, etc.)?

Use dative pronouns:

мне (to me)
тебе (to you, informal)
ему / ей (to him / to her)
нам (to us)
вам (to you, pl/formal)
им (to them)
Example: Им вредно пить газировку каждый день.

How is the stress and pronunciation?

мне [mnʲe] (one syllable)
врЕдно [ˈvrʲednə] (stress on the first syllable)
пить [pʲitʲ] (soft ть)
газирОвку [gəzʲɪˈrofku] (stress on О)
кАждый [ˈkaʐdɨj] (stress on the first syllable)
день [dʲenʲ]

How do I negate this?

Мне не вредно пить газировку каждый день. = “It’s not harmful for me to drink soda every day.”
Не пить газировку мне вредно. = “Not drinking soda is harmful to me” (grammatically fine, but odd logically).
Negation typically goes on вредно: не вредно.

Is сода a correct word for “soda” (soft drink) in Russian?

Be careful: сода usually means baking soda. For soft drinks, use газировка or газированные напитки. For soda water specifically: газированная вода or содовая. Brand-specific: кола, лимонад (often any lemon-lime soda), etc.

Are there alternatives to каждый день?

Yes:

ежедневно (more formal).
Colloquial emphasis: каждый божий день.
You can adapt the pattern: каждую неделю, каждое утро, через день, etc.

Why not say something like Я вредный пить газировку каждый день?

Because вредный describes a person/thing as “harmful” or “nasty” (e.g., “I’m a mean person”), not that an action is harmful to you. To evaluate an activity’s effect on you, Russian uses the impersonal predicative with dative: Мне вредно (что делать?) пить…