Мало того что в булочной не было ватрушки, так ещё и мой любимый бублик закончился.

It is a fixed contrastive pattern meaning something like:

• Not only ... but on top of that ...
• As if ... weren’t enough, ...
• To make matters worse, ...

In this sentence, the speaker is complaining that one bad thing happened, and then another disappointing thing happened too.

So the structure is:

• мало того что X, так ещё и Y

where X is the first problem and Y is the extra problem.

Because мало того что is part of the set expression.

You should usually learn it as one chunk:

• мало того что ...
• так ещё и ...

Literally, что here introduces the first clause, somewhat like that in older or more formal English patterns. But in practice, it is best not to translate each word separately. Just remember the whole frame.

Here так helps connect the second clause to the first. It reinforces the idea of escalation:

• first bad thing: в булочной не было ватрушки
• second bad thing: так ещё и мой любимый бублик закончился

In this structure, так ещё и is very common and natural. It gives the sense of and to make things even worse...

So although так often means so or thus, here it is part of the idiomatic linking pattern.

Ещё и means also, even, or on top of that, depending on context.

In this sentence it makes the complaint stronger. Without it, the sentence would still work, but it would sound less expressive.

Compare:

• ..., так и мой любимый бублик закончился. — less idiomatic here
• ..., так ещё и мой любимый бублик закончился. — natural, emphatic, and on top of that my favorite bagel was sold out

So ещё и adds the feeling of an additional annoyance.

Because в meaning in / at takes the prepositional case when talking about location.

The dictionary form is:

• булочная = bakery / bread shop

Prepositional singular:

• в булочной = in the bakery / at the bakery

So:

• булочная → base form
• в булочной → location

They are related, but not always exactly the same.

• булочная usually means a bread shop or bakery shop, a place where bread and pastries are sold
• пекарня usually means a bakery as a place where things are baked, though it can also be used for a shop

In this sentence, в булочной strongly suggests the speaker is talking about a shop they went to.

This is the common Russian pattern for saying that something wasn’t there or didn’t exist in a place:

• не было + genitive

It uses the past tense of быть in the neuter singular form было, in an impersonal existential construction.

Examples:

• В магазине не было хлеба. = There was no bread in the store.
• На столе не было книги. = There was no book on the table.

So в булочной не было ватрушки means there was no vatruška at the bakery.

This is not about grammatical agreement with ватрушка. It is a standard existential pattern.

Because after не было in this existential meaning, Russian normally uses the genitive for the thing that was absent.

Dictionary form:

• ватрушка = nominative singular

Genitive singular:

• ватрушки

So:

• не было ватрушки = there was no vatruška

This is very common in Russian:

• не было времени = there was no time
• не было денег = there was no money
• не было молока = there was no milk

Because the two clauses use different grammatical structures.

First clause:

• в булочной не было ватрушки
• This is an existential negative construction: there was no ...
• That is why ватрушки is in the genitive

Second clause:

• мой любимый бублик закончился
• Here бублик is the subject of the verb закончился
• Subjects are normally in the nominative

So the cases are different because the grammar of the two clauses is different.

Yes, literally it comes from закончиться, meaning to come to an end, to be finished, or to run out.

In the context of food in a shop, закончился usually means:

• was sold out
• ran out

So:

• мой любимый бублик закончился = my favorite bagel was sold out / had run out

Russian often uses закончиться this way for items that are no longer available.

Because it agrees with бублик, which is:

• masculine
• singular
• nominative

Past tense verbs in Russian agree in gender and number:

• masculine: закончился
• feminine: закончилась
• neuter: закончилось
• plural: закончились

Since бублик is masculine singular, the verb must be закончился.

The verb is закончиться, not закончить.

Very roughly:

• закончить = to finish something
• закончиться = to finish / come to an end / run out

So:

• Магазин закончил работу. = The store finished work.
• Хлеб закончился. = The bread ran out.

In this sentence, the reflexive form -ся helps make бублик the thing that ran out / was no longer available, rather than something actively finishing another object.

Here и adds emphasis and helps tie the extra item more tightly into the complaint.

• ещё = still / more / else / additional
• ещё и = and also / and even / on top of that

In emotional speech, ещё и is very common when the speaker feels annoyed or surprised by the extra problem.

No. It sounds like a mild complaint or frustration.

The structure мало того что ... так ещё и ... strongly suggests that the speaker is piling up disappointments:

1. there was no ватрушка
2. and then, even worse, the favorite бублик was sold out too

So the tone is natural for complaining, grumbling, or telling someone about bad luck.

Yes, Russian word order is flexible, but this version is very natural.

For example, you could sometimes move parts around for emphasis, but the fixed frame usually stays recognizable:

• Мало того что в булочной не было ватрушки, так ещё и мой любимый бублик закончился.

This order sounds smooth because:

• the first problem is stated first
• the second, more personal disappointment comes after it
• мой любимый right before бублик makes the second problem feel especially important emotionally

So while some variation is possible, this word order is a good standard model.

They are both baked goods.

• ватрушка: a pastry, often round, usually with a filling such as sweetened cottage cheese
• бублик: a ring-shaped bread product, similar in shape to a bagel, though not always exactly the same as an American-style bagel

A native English speaker may not know these foods, so it is often best to treat them as culture-specific bakery items rather than expect a perfect one-word English match.

Yes. It sounds natural and idiomatic.

A native speaker might use this exact type of sentence when talking about an annoying shopping experience, for example:

• Мало того что автобус опоздал, так ещё и дождь начался.
• Мало того что я забыл кошелёк, так ещё и телефон сел.

So this sentence is a good example of a very common Russian way to stack complaints.