Learn Hardcore Ukrainian: Бутерброд із сиром і яйцем дуже смачний. - The sandwich with cheese and egg is very tasty.

In Ukrainian, the preposition meaning “with” is з/із/зі, and it governs the instrumental case: із ким? із чим? — “with whom? with what?” Hence, із сиром і яйцем = “with cheese and egg.”

Why is it із and not з or зі?

Ukrainian has euphonic variants з / із / зі. The choice is made for ease of pronunciation:

із is used before certain consonants or clusters to avoid awkward combinations. Before words starting with с, ш, ж, з etc., із is common. Hence, із сиром is smoother than з сиром.
зі appears before some clusters (e.g., зі школи, зі мною, зі святом).

Here, із сиром is the natural choice. Saying з сиром isn’t grammatically wrong, but it’s less euphonic. Зі сиром is not idiomatic here.

Why is the conjunction і used and not й (or та)?

і is the default “and.”
й is often used between two vowels to avoid a hiatus: e.g., кава й апельсин. After a consonant, і is standard: сиром і яйцем (the preceding word ends with a consonant).
та also means “and” and can be used for variety or euphony: із сиром та яйцем. It’s stylistic, not required.

Why is the adjective смачний (masculine) and not смачна/смачне/смачні?

Adjectives agree with the noun in gender, number, and case. Бутерброд is masculine singular nominative, so the predicate adjective is masculine singular nominative: дуже смачний.

Feminine: смачна
Neuter: смачне
Plural: смачні

Could I say дуже смачно instead of дуже смачний?

Yes, but it changes the structure:

Бутерброд … дуже смачний. (adjective agreeing with the noun)
Це дуже смачно. (impersonal/adverbial comment “This is very tasty.”)

In your sentence, because you name the noun (бутерброд), the adjective form смачний is the natural match.

Where is the verb “is”? Do we need є?

Ukrainian usually omits the present tense of “to be” (є) in simple “X is Y” sentences. So:

Бутерброд … дуже смачний. = “The sandwich is very tasty.”

You can insert є for emphasis or formality. With є, speakers often use the instrumental in the predicate to highlight a quality or state:

Бутерброд … є дуже смачним. Both nominative (смачний) and instrumental (смачним) occur; without є, stick to nominative.

Should it be яйцем (singular) or яйцями (plural)?

Both are possible, depending on meaning:

із сиром і яйцем treats the ingredients as types/substances (the usual menu wording).
із сиром і яйцями emphasizes multiple eggs (e.g., visible slices/pieces). For a typical “cheese-and-egg sandwich,” singular is more common.

Could I use the genitive, like бутерброд із сира та яйця?

That shifts the meaning. З/із/зі with the genitive commonly means “from/out of” or “made of” (material): стіл із дуба = “a table made of oak.” For “with” (ingredients, accompaniment), use instrumental: із сиром і яйцем. You may repeat the preposition for style: із сиром і з яйцем, but it’s not necessary.

What are the base forms and genders of the nouns here?

бутерброд (masc., nominative singular) — “sandwich”
сир (masc., nominative singular) — “cheese”
яйце (neut., nominative singular) — “egg”

Where is the stress and how do I pronounce the tricky vowels?

бутерброд: stress on the last syllable — бутербро́д.
сиром: stress on the first syllable — сИром.
яйцем: stress on the second syllable — яйце́м.
дуже: ду́же.
смачний: смачни́й.

Vowel tip: і = close “ee” sound; и = a more central “i” (not the same as English “i”). So сиром is not like English “seerom”; it’s closer to [SY-rom], with a short, central vowel for и.

Can I change the word order?

Yes; Ukrainian allows flexible word order for emphasis:

Дуже смачний бутерброд із сиром і яйцем. (emphasizes “very tasty”)
Бутерброд дуже смачний — із сиром і яйцем. (afterthought of ingredients) All are fine; the original is neutral and natural.

How do I make the whole sentence plural?

Singular: Бутерброд із сиром і яйцем дуже смачний.
Plural: Бутерброди із сиром і яйцем дуже смачні. If you want plural eggs explicitly: Бутерброди із сиром і яйцями дуже смачні.

Is бутерброд the same as сендвіч or канапка?

They overlap but have nuances:

бутерброд: broad, traditional term (often open-faced in older usage, but widely used for any sandwich).
сендвіч: a calque from English; often two slices of bread with filling (closed sandwich).
канапка: common in western/colloquial Ukrainian; typically a small open-faced sandwich. In everyday speech, бутерброд is very common and perfectly fine here.

Do I need to repeat the preposition before the second ingredient?

No. One preposition covers coordinated nouns in the same case:

Standard: із сиром і яйцем
Optional (for rhythm/emphasis): із сиром і з яйцем

Why is it яйцем and not Russian-like яйцом?

Ukrainian endings differ from Russian. The instrumental singular of neuter -це nouns is -цем in Ukrainian: яйце → яйцем (not яйцом).

Is there any difference in meaning between із сиром and з сиром?

No semantic difference—both mean “with cheese.” The choice is euphonic. Before с in сиром, із sounds smoother and is the recommended form here.