kyou no asagohan ha toosuto to orenzi desu.

It is read:

きょう の あさごはん は トースト と オレンジ です。

A few notes:

• 今日 = きょう
• 朝ご飯 = あさごはん
• トースト = toosuto
• オレンジ = orenji

In normal Japanese writing, it would usually appear without spaces: 今日の朝ご飯はトーストとオレンジです。

の connects nouns.

Here, 今日 and 朝ご飯 are both noun-like, and の links them so that 今日 modifies 朝ご飯:

• 今日 = today
• 朝ご飯 = breakfast
• 今日の朝ご飯 = today’s breakfast

So の is doing the job of English ’s or sometimes of.

は marks the topic of the sentence.

The topic is the whole phrase:

今日の朝ご飯は = As for today’s breakfast, ...

Then the rest of the sentence says what it is:

トーストとオレンジです = it is toast and orange(s)

So the structure is basically:

[topic] は [comment] です

Because the topic is not just today. The topic is the whole noun phrase 今日の朝ご飯.

Compare:

• 今日の朝ご飯は... = As for today’s breakfast...
• 今日は... = As for today...

Those are different topics.
In this sentence, the speaker wants to talk specifically about today’s breakfast, not just today in general.

と is used to join nouns in a complete list. Here it works like and.

So:

• トーストとオレンジ = toast and orange(s)

This use of と sounds like a straightforward list of the items.

Because トーストとオレンジ is the predicate noun phrase before です.

This is not an action sentence like I eat toast.
It is an X is Y sentence:

• 今日の朝ご飯は = the topic
• トーストとオレンジです = what it is

So there is no need for an object particle like を.

This is a very common question.

In words like:

• 朝ご飯 = breakfast
• 昼ご飯 = lunch
• 晩ご飯 / 夜ご飯 = dinner

ご飯 does not always mean literal cooked rice. It can also mean a meal.

So 朝ご飯 means breakfast even if the meal is toast, eggs, cereal, or anything else.

Katakana is often used for:

• loanwords from other languages
• foreign-sounding words
• some food names and product names

Here:

• トースト comes from toast
• オレンジ comes from orange

So katakana is the normal writing choice.

In this sentence, 今日 is read きょう.

That is the normal reading when it means today in everyday speech.

The reading こんにち exists, but it is used in more limited contexts, such as certain formal or set expressions. In this sentence, こんにち would not be correct.

です is the polite copula. It works like is / am / are in this kind of sentence.

So トーストとオレンジです means it is toast and orange(s).

In casual speech, です may be omitted:

• 今日の朝ご飯はトーストとオレンジ。

That sounds more casual and conversational.

Yes, it is natural.

It is a simple and clear sentence for saying what today’s breakfast is.

Some natural variations are:

• 今日の朝ご飯はトーストとオレンジです。
  Neutral and polite.

• 今日の朝食はトーストとオレンジです。
  More formal because 朝食 is more formal than 朝ご飯.

• 今朝はトーストとオレンジでした。
  More like This morning, I had toast and orange(s), depending on context.

So the original sentence is perfectly fine, but Japanese offers slightly different ways to express the same idea.

No. Standard Japanese normally does not use spaces between words.

So this sentence would usually be written as:

今日の朝ご飯はトーストとオレンジです。

Spaces are often added in beginner materials to make the structure easier to see.