Ein Hustenbonbon in der Tasche ist praktisch, besonders wenn mein Hals im Zug trocken wird.

Because Hustenbonbon is a neuter noun: das Hustenbonbon.

So in the nominative singular, the indefinite article is ein:

• ein Hustenbonbon
• compare:
  • ein Tisch (masculine)
  • eine Tasche (feminine)
  • ein Bonbon (neuter)

Also, Hustenbonbon is a compound noun:

• Husten = cough
• Bonbon = candy / sweet

So literally it is something like cough candy, usually meaning a cough drop or throat sweet.

Because this phrase describes location, not movement.

German uses different cases after certain prepositions like in:

• dative for where?
• accusative for where to?

Here, the candy is in the pocket/bag already, so it is a static location:

• in der Tasche = in the bag / in the pocket

Compare:

• Das Bonbon ist in der Tasche. = The candy is in the pocket.
• Ich stecke das Bonbon in die Tasche. = I put the candy into the pocket.

Since Tasche is feminine, the dative form is der Tasche.

Tasche can mean bag, pocket, or sometimes a pouch-like container depending on context.

So in der Tasche could mean:

• in my pocket
• in my bag
• in a pocket of a coat or backpack

German often leaves this slightly general unless the context makes it specific. A learner should not assume it always means only bag.

This is a normal German main clause, and in main clauses the finite verb usually goes in second position.

The whole subject is:

• Ein Hustenbonbon in der Tasche

Then the verb comes:

• ist

Then the adjective:

• praktisch

So the structure is:

• [Subject] + [finite verb] + [rest]

German counts the whole initial subject phrase as one unit, even though it contains several words.

Because praktisch is being used as a predicate adjective, after the verb sein.

In German, adjectives used after sein, werden, or bleiben usually do not take adjective endings:

• Das ist praktisch.
• Der Hals wird trocken.
• Das Bonbon ist gut.

Adjective endings appear when the adjective comes before a noun:

• ein praktisches Bonbon
• ein trockener Hals

So here, praktisch stays in its basic form.

Wenn here means when in the sense of whenever / if and when.

The idea is:

• a cough drop is useful, especially when my throat gets dry on the train

German wenn is commonly used for:

1. repeated or general when
2. conditional if

Examples:

• Wenn ich müde bin, trinke ich Kaffee. = When / If I’m tired, I drink coffee.
• Wenn es regnet, bleiben wir zu Hause. = If it rains, we stay home.

In this sentence, wenn introduces a subordinate clause.

Because wenn introduces a subordinate clause, and in German subordinate clauses the conjugated verb usually goes to the end.

So:

• wenn = subordinating conjunction
• mein Hals = subject
• im Zug = prepositional phrase
• trocken = adjective
• wird = verb at the end

This is a very important German pattern:

• Ich komme, wenn ich Zeit habe.
• Sie bleibt zu Hause, weil sie krank ist.
• Er ruft an, wenn er fertig ist.

So wird moves to the end because of wenn.

German often uses a possessive where English might also do so naturally: my throat.

So:

• mein Hals = my throat

This is completely normal. German can also use a definite article with body parts in some contexts, especially when the owner is already clear:

• Mir tut der Hals weh. = My throat hurts.
  Literally: The throat hurts to me.

But in this sentence, mein Hals is straightforward and natural.

Im is simply the contraction of in dem.

• in dem Zug → im Zug

This contraction is very common and usually preferred in normal speech and writing.

So:

• im Zug = in the train / on the train

German often uses in with forms of transport where English would often say on:

• im Zug = on the train
• im Bus = on the bus
• im Auto = in the car

Because wird means becomes / gets, not just is.

So:

• trocken ist = is dry
• trocken wird = becomes dry / gets dry

The sentence is talking about a change of state:

• your throat starts out normal
• then it gets dry

This is why werden is the right verb here.

A very common pattern is:

• müde werden = get tired
• krank werden = get sick
• nervös werden = become nervous
• trocken werden = get dry

Not exactly a fixed idiom, but it is a very common combination.

• besonders = especially
• wenn = when / if

Together they mean:

• especially when ...

It is a natural way to add a specific situation in which something is especially true.

Examples:

• Kaffee ist gut, besonders wenn es kalt ist.
• Ein Regenschirm ist praktisch, besonders wenn es regnet.

So in your sentence, it highlights the situation in which the cough drop is especially useful.

Yes. In real usage, Hustenbonbon often refers broadly to a cough drop or soothing candy for the throat, even if the issue is dryness or irritation rather than an actual cough.

German compound nouns are often a bit broader in real-life meaning than their literal parts suggest. So even though Husten means cough, the word can still fit naturally in a sentence about a dry throat.

The sentence has:

1. a main clause
2. a subordinate clause introduced by wenn

Breakdown:

• Ein Hustenbonbon in der Tasche ist praktisch,

  • subject: Ein Hustenbonbon in der Tasche
  • verb: ist
  • complement: praktisch

• besonders wenn mein Hals im Zug trocken wird.

  • besonders modifies the whole idea
  • wenn introduces the subordinate clause
  • verb wird goes to the end

So the pattern is:

• Main clause + especially + subordinate clause

This is a very common German sentence type.