We’ll have two hamburgers and two large cokes.

[Alice Chu]

We use “I or we” for “instant decisions”
1) I’ll have a big bowl of beef noodles, please.
2) We’ll have two hamburgers and two large cokes.

 

[Charlie Bernstein]

We use “I" or "we” for [STRIKE]“[/STRIKE]instant decisions[STRIKE]"[/STRIKE]:

That's true. We use them for lots of things. But there is nothing special about instant decisions.

1) I’ll have a big bowl of beef noodles, please.
2) We’ll have two hamburgers and two large cokes.

What's your question?

 

[emsr2d2]

I don't understand why you think that "I" or "We" has anything to do with instant decisions. The timing of a decision is irrelevant to the choice of pronoun.
Both your examples could be used when someone has made an instant decision but it's equally possible that they've been pondering the menu for ages before actually ordering.

 

[Rover_KE]

In writing, you need to capitalise 'Cokes' as it's short for Coca-Cola.

 

[Phaedrus]

. . . and two large cokes.

. . . and two large Cokes.

Coke being a brand name, it should be capitalized. Similarly, in the expanded form, we would write two large Coca-Colas, not two large coca-colas.

(This was cross-posted with Rover's post above. )

 

[emsr2d2]

And if you're ordering a generic form of Coca-Cola, call it a "cola".

 

[Alice Chu]

Are the subjects limited to “I” or “we” when we use “will” to express a spontaneous decision (an instant decision)?
[h=3]https://www.ef.co.uk/english-resources/english-grammar/simple-future-tense/[/h]

• With I or We, to express a spontaneous decision:
  I'll pay for the tickets by credit card.

 

[5jj]

Are the subjects limited to “I” or “we” when we use “will” to express a spontaneous decision (an instant decision)?

Yes, when we are talking about who is making the decision; not always if we are talking about the grammatical subject of the verb.

Damn! I've got meetings scheduled tomorrow in two different places. What shall I do? I know! I'll go to the Paris meeting and John'll go to Berlin for me.

 

[Tdol]

You could make the decision for someone else, though.

A: I'll have a hamburger.
B: What about your friend?
A: She'll have the same.