Tea vs a tea

A. Can I have tea, please? OK

B. I'll have tea, please. OK (better)

C. Can I have a tea, please? No. You can say "a cup of tea".
D. I'll have a tea, please.

Thank you, AlpheccaStars. This is clear to me now.

I see 'a tea' is not correct. I thought an uncountable noun can be used with an indefinite article implying a meaning like 'a cup of tea' in the example, but I was wrong. Would you say, then, that the examples below are not correct? I hear these sometimes.

I'll have a Coke, please.
I'll have an or

Anon:

Yes, you will hear those expressions sometimes.

I'll have a Coke, please. Coke used to be sold only in distinctive specially-shaped bottles. So asking for "a coke" was asking for one of these, and it just caught on. At the fountain, I say "I'll have (a medium (sized)) Coke."
I'll have an orange juice, please.

Thanks, again, for your response.

I'm just confused, why "a tea" is not correct when "a Coke" and "an orange juice" are correct. Would "a tea" be correct if it was on the menu?

By the way, which is common?
I'll have a Coke. or
I'll have Coke.

As I said, it is based on history when Coke used to come in Coca-Cola bottles. When you ordered "a coke" you didn't mean an amount of liquid, you mean a chilled bottle with the liquid inside. These days, you almost never see the classic coca-cola bottles.
But the old way of ordering it has stayed in the culture - I'll have a coke.

Tea never came in bottles; it was bre

Perhaps for the first time, I disagree with A Stars.
I would easily interpret "a tea" as a cup/glass of tea.

When I was waitressing the breakfast shift, it was common enough to get an order for "two coffees and a tea" or "two teas and a coffee" (or whatever combination). (At breakfast, "a tea" would get you hot tea.)

(Once it was the lunch shift, "two Cokes and a tea" would

GG:

That's interesting, because I consider "tea" to be non-count and have always ordered "a glass of iced tea/iced tea," "a cup of hot tea/hot tea," or "a pot of tea."

I suppose if you're in the waitressing business, there would be lots of short cuts - "two teas" glides much faster off the tongue than "two glasses/cups of tea."

Did you ever get an order for "a water?"

You bet.

I'd just like a water, please.

Not just when I was waitressing, but just about every time I eat out.

Does that really seem so unnatural to you? Regional?

GG;
It does sound strange, actually.
I do say - a coke, because it used to come in bottle-sized servings, but water?

I'd say - I'll just have water, thanks. or Please bring me some water.
Maybe it's just me, though!

Thank you, A-s and GG, for your explanations.

From your exchanges, I've come to the conclusion that "a tea or two teas", "