Vişne suyu çok ekşi olunca kız kardeşim biraz şeker ekledi.

Not exactly. Vişne means sour cherry or morello cherry, not the sweet cherry you would usually call kiraz in Turkish.

So:

• vişne = sour cherry
• kiraz = sweet cherry

That is why vişne suyu is specifically sour cherry juice.

This is a very common Turkish noun-compound pattern.

When one noun describes another noun, the second noun usually takes a compound marker that looks like a 3rd-person possessive ending. So:

• elma suyu = apple juice
• portakal suyu = orange juice
• vişne suyu = sour cherry juice

So vişne suyu literally looks something like its sour-cherry water/juice, but in normal English you should simply understand it as sour cherry juice.

Also, su is a slightly irregular word. In compounds and possessive forms, it becomes suyu.

Olunca comes from olmak, which is a very common verb meaning to be, to become, or to happen, depending on context.

Here is the breakdown:

• ol- = verb stem
• -unca = a suffix meaning when, once, after, or sometimes because

So olunca means something like:

• when it was
• when it became
• since it was
• because it was

In this sentence, çok ekşi olunca means when/since it was very sour.

Grammatically, -ınca / -ince / -unca / -ünce often means when or once. But in real sentences it can also feel like because if the first action clearly causes the second.

So here:

• Vişne suyu çok ekşi olunca...
  can be understood as
  When the sour cherry juice was very sour...
• but in natural English, it may be better as
  Because the sour cherry juice was very sour...

So the Turkish form is the same, but English may translate it in different ways depending on the context.

Because Turkish often uses olmak with adjectives when building certain subordinate clauses.

You can say:

• Vişne suyu çok ekşi. = The sour cherry juice is very sour.

But to make a clause like when it was sour or since it was sour, Turkish commonly uses:

• ekşi olunca

So in this sentence:

• çok ekşi olunca = when/since it was very sour

It does not always mean a dramatic change like became sour. Very often it just helps form the clause naturally.

Yes.

Breakdown:

• kız kardeş = sister, literally female sibling
• -im = my

So:

• kız kardeşim = my sister

Related forms:

• kız kardeşin = your sister
• kız kardeşi = his/her sister
• erkek kardeş = brother, literally male sibling

Because Turkish usually shows possession with a suffix, not a separate word like English my.

So instead of saying something like my sister, Turkish often puts the possession directly on the noun:

• kardeş = sibling
• kardeşim = my sibling
• kız kardeşim = my sister

Turkish does have independent pronouns like benim for my/mine, but they are not always necessary. In a simple sentence like this, the suffix alone is enough.

Because the object is indefinite and non-specific.

In Turkish, a direct object often stays without the accusative if it means some, a certain amount of, or an unspecific object.

So:

• biraz şeker ekledi = she added some sugar

Here şeker is a non-specific amount, so no accusative is used.

Compare:

• şeker ekledi = added sugar / some sugar
• biraz şeker ekledi = added a little sugar
• şekeri ekledi = added the sugar / added a specific sugar

So the lack of accusative here is completely normal.

Biraz means a little, a bit, or some.

In this sentence:

• biraz şeker = a little sugar / some sugar

It is a very common word for small amounts.

Examples:

• biraz su = a little water
• biraz bekle = wait a little
• biraz yorgunum = I’m a little tired

Ekledi comes from eklemek, meaning to add.

Breakdown:

• ekle- = add
• -di = past tense

So:

• ekledi = he/she/it added

There is no extra ending here for she because Turkish 3rd-person singular is often just the bare past-tense verb form.

Because Turkish often leaves out subject pronouns when they are already clear from context.

In this sentence, the subject is explicitly stated as:

• kız kardeşim = my sister

So adding o (she) would usually be unnecessary.

Turkish prefers not to repeat information if the subject is already obvious.

Yes. It is very natural.

Turkish often places a time, condition, or reason clause near the beginning, and the main verb usually comes at the end.

So the structure is:

• Vişne suyu çok ekşi olunca = when/since the sour cherry juice was very sour
• kız kardeşim = my sister
• biraz şeker = a little sugar
• ekledi = added

So the overall pattern is very Turkish:

[background/reason clause] + [subject] + [object] + [verb]

Literally, çok ekşi means very sour.

• çok = very
• ekşi = sour

But in context, English might sometimes translate it as too sour, because the sourness caused an action: adding sugar.

So:

• literal meaning: very sour
• context-based translation: sometimes too sour

Turkish does not always mark that distinction as explicitly as English does.

Yes. For example, you might also hear:

• Vişne suyu çok ekşiyken kız kardeşim biraz şeker ekledi.

That would mean something like:

• While the sour cherry juice was very sour, my sister added some sugar
• or more naturally, Since the sour cherry juice was very sour, my sister added some sugar

But olunca is very natural here because it connects the first situation to the result that follows. It often sounds like once it was like that / since it was like that.