The first sip of milk is an uncountable noun, so it is wrong to use some. In the second negative sentence, replace some with any. The specific usage is as follows:

In general, some is used for affirmative sentences and any is used for negative sentences and interrogative sentences. For example:

There are some letters for you. There are some letters for you.

There is no letter for you. None of them are yours.

Is there any letter for me? Is there any letter for me?

However, in the following special cases, you usually use some instead of any:

1. Questions that want an affirmative answer usually use some. For example:

May I have some paper? Can I get some paper?

Didn't he give you some money? Didn't he give you some money?

Can you lend me some money? Can you lend me some money?

Aren't there some stamps in that drawer? Aren't there some stamps in that drawer?

2.some is usually used in interrogative sentences expressing requests or suggestions. For example:

Why not give her some flowers? Why not send her some flowers?

Do you want some bananas? Do you want some bananas?

Won't you eat some more? Don't you want some more?

Shall I get you some chalk? Shall I get you some chalk?

Sometimes some can be used in both affirmative and negative sentences, but their meanings are different. For example:

I don't like some movies. I don't like some of these movies.

I don't like any of these movies. I don't like any of these movies.

4. Used with less or less, it means negative meaning, positive meaning, "quite a lot" and "quite a lot". For example:

Some students are absent today. Many students are absent today.

He spent a little money on books. He spent a lot of money on books.

Note: Don't interpret some less/some less as "quite less".

From: /diary/ 164509/