Questions about Japanese language

1) Normally, how to ask a person if he can help me a take picture?
Is it 写真を撮ることはできますか？or 写真を撮っていただけますか？ or any other sentences? I would like to know

2) At the cafe(Tokyo),the clerk asked what drinks would you like to have? In Japanese, how many ways can they ask as I don't seem to recall them using 飲み物.....Thank you

写真を撮ることはできますか？

することができる means literally , are you physically capable of doing something. Eg can you swim... so with a photo it sounds odd unless you have a very specific situation. Eg you ask a blind person.

or 写真を撮っていただけますか？
Vていただける、Vてもらえる、Vてくれる all mean to receive the action , in this case the photo taking , from someone. These firms are different kind of politeness levels, being Vていただける the most polite. Note that いただける & もらえる are the potential (ie can-forms) of いただく＆もらう. So literally it means, could I receive the favor to have a picture taken.

I am sure there are other ways how to ask for a picture, but with strangers I use 写真を撮っていただけますか。or even more polite 写真を撮っていただけませんか。the negative form would means something on the line of : if you wouldn’t mind, could you take a picture? A literal translation into English does not really make sense as negation in English works differently.

Enjoy studying Japanese!

2)
They might have said "ドリンク" (obviously from "drink") or "お飲み物" ("o" added) for the word "drink." Or they could have asked if you are ready to order :)

When it comes to the sentence, they could also ask in different ways, like "what would you like for your drink?" "are you ready to order a drink?", "what do you want to do drink-wise?" etc.

- お飲み物は何にしますか。
- お飲み物は何になさいますか。
- お飲み物のご注文はよろしいですか
- お飲み物の方はどうしますか
- お飲み物はいかがなさいますか, etc. (and you can replace "o-nomimono" with "dorinku")

Normally, how to ask a person if he can help me a take picture?

What do you precisely mean? The expression depends on who is pressing the shutter, who is using whose camera, and what the photographer is shooting.

@Uco, What I meant is if I approach someone and ask if the person can help to take a picture of me....

Black Joker,

Who is pressing the shutter?
Whose camera is being used?
What do you want to take the picture of?

@Uco, Okay....I meant I want a picture of myself to be taken at a spot. So I would randomly approach someone and ask the man/woman if he/she could help me a take picture? if he/she says okay, he/she would help, I would then hand my phone over to him/her, he/she would use my phone to take a picture of me.....

Then you can say...
写真を撮っていただけますか？
(Could you take a photo for me?)

To clarify, you can also use the more common expression...
シャッターを押していただけますか？
(Could you press the shutter [of my camera] for me [and take a photo of me/us]?)

Meanwhile...
写真を撮ることはできますか？
only means "Is it possible to take photos?"
So it doesn't say anything about who is talking the photo for whom.
This expression is more commonly used when asking permission to take photos.
So it's more used when you want to say,
"Am I allowed to take photos here?"
such as when you're in a museum or store where photography is often prohibited.

I hope this answered your question.

In the real world, if you have somebody take a photo of you by your camera, you point at your camera or show your camera as if hand out and say "onegai dekimasuka?- Can you please?"

hand out and say

That's a really good idea, and it reminds me of misunderstandings I hear too often on TV. When you approach a person who is a little bit famous but not as noticeable, such as a TV star who isn't a star any more or too local to be known internationally, the person may misinterpret that you want to take a photo with that person in your photo. It's always best to clarify who is going to hold that camera for you.