shuìdài zài bēibāo lǐ, kěyǐ bǎonuǎn.

In this sentence, 在 is used in the pattern Subject + 在 + Place to say where something is.

So:

• 睡袋在背包里 = The sleeping bag is in the backpack

This is the normal way to state location in Mandarin.

If you start with 在背包里, that usually sounds like you are setting the scene first, and you would normally continue with a fuller sentence, such as:

• 在背包里有一个睡袋 = There is a sleeping bag in the backpack

So 睡袋在背包里 is a straightforward location sentence.

Here, 在 means to be located at/in.

It is not the progressive marker like in 我在吃饭.
In this sentence, it is part of a location statement:

• 睡袋在背包里 = The sleeping bag is in the backpack

So here 在 functions like is at / is in.

里 means inside.

So:

• 背包 = backpack
• 背包里 = inside the backpack

With container nouns like 背包, 箱子, 房间, using 里 is very common because it clearly shows that something is inside.

You may also see:

• 背包里面

This means the same thing, just a little fuller.

Yes. Both are natural.

• 背包里 = common, concise
• 背包里面 = slightly more explicit or fuller

So these are both fine:

• 睡袋在背包里。
• 睡袋在背包里面。

The version with 里 is a little shorter and very common in everyday speech.

The comma separates two related parts:

• 睡袋在背包里
• 可以保暖

The subject of the second part is understood from the first part. In other words, Mandarin often leaves out repeated words when they are obvious.

So the full idea is roughly:

• 睡袋在背包里，睡袋可以保暖。

But repeating 睡袋 would sound unnecessary, so it is omitted.

The understood subject is 睡袋.

So:

• 睡袋在背包里，可以保暖。
• literally: The sleeping bag is in the backpack, and can keep warm / keep one warm

Mandarin often drops subjects when they are already clear from context.

So even though 睡袋 is not repeated, it is still understood as the subject of 可以保暖.

No. Here 可以 does not mean permission.

It means something like:

• can
• is able to
• can be used to

So in this sentence, 可以保暖 means the sleeping bag can keep you warm or can provide warmth.

This is about function or usefulness, not permission.

保暖 means to keep warm or to preserve warmth.

It is commonly used when talking about clothes, blankets, sleeping bags, and weather.

Examples:

• 多穿一点衣服保暖。 = Wear more clothes to keep warm.
• 这件外套很保暖。 = This coat is very warm / good for keeping warm.

In your sentence, 可以保暖 means the sleeping bag can help maintain warmth.

Because Mandarin often leaves out objects and pronouns when they are understood from context.

In English, we often say:

• It can keep you warm

In Mandarin, it is very natural to just say:

• 可以保暖

The person being kept warm is understood generally, so it does not have to be said.

If you want to make it explicit, you could say:

• 睡袋可以帮你保暖。 = A sleeping bag can help keep you warm.

Yes, but the focus changes.

• 睡袋在背包里 focuses on the location of the sleeping bag
• 背包里有睡袋 focuses on the existence of a sleeping bag in the backpack

So:

• 睡袋在背包里，可以保暖。 = The sleeping bag is in the backpack; it can keep you warm.
• 背包里有睡袋，可以保暖。 = There is a sleeping bag in the backpack; it can keep you warm.

Both are possible, but they present the information differently.

Grammatically, it says both:

• the sleeping bag is in the backpack
• it can keep warm

So the sentence combines location and function.

In real-life context, it may sound a little compressed in English, because English often prefers something like:

• There is a sleeping bag in the backpack. It can keep you warm.

Mandarin is comfortable putting those two ideas together in one sentence.

Yes.

• 睡 = sleep
• 袋 = bag / sack

So 睡袋 is a very transparent compound word, just like many Mandarin nouns.

This kind of word-building is very common in Chinese:

• 书包 = book bag = schoolbag
• 火车 = fire vehicle = train
• 手表 = hand watch = wristwatch

Both can work, but there is a slight nuance.

• 可以保暖 often suggests it can be used to keep warm or it serves the purpose of keeping warm
• 能保暖 often emphasizes ability/effectiveness

In this sentence, 可以保暖 sounds natural because you are describing the sleeping bag’s practical function.

So 可以保暖 is a good choice here.

Yes. A measure word is not needed here because 睡袋 is being used as a general noun or as a known item in context.

You need a measure word when counting or specifying:

• 一个睡袋 = one sleeping bag

But in your sentence, you are simply talking about the sleeping bag or sleeping bags in general, so 睡袋 by itself is fine.

At a beginner level, it is easiest to treat 睡袋 as the subject of the first clause:

• 睡袋在背包里

In the second clause, the subject is omitted but still understood to be 睡袋:

• 睡袋可以保暖

From a more advanced point of view, you could also say 睡袋 acts as the topic for the whole sentence, with the rest saying something about it. But for most learners, thinking of it as the subject is perfectly helpful and accurate enough here.