Question

Is it proper to write "I want 2 teas please"?

Answer 1

In contemporary English, no.

Explanation:

When we want to use the plural for tea, considering tea is a cup of it, we would ask for two cups of tea.

This could change if you were in a cafe, for instance. You may be able to ask for two teas or coffees or waters and they'd give it to you because they know what you're speaking of.

When we reference water, we usually ask for bottles of water. We use the plural of the container or order we use before the drink.

Two orders of tea.
Two cups of tea.

Those are perfectly fine to use in any situation.

Answer 2

This answers if using a numeral before a noun is appropriate in English:

Explanation:

I'm answering the question for whether a numeral can used before a noun, such as 2 teas.

In general, numbers are written out up to the point where the number gets to be so big that a numeral is more useful. That limit tends to be in the thousands to ten thousands range (at least from what I remember of this).

And so, while this is not correct:

I ordered 2 teas during breakfast.,

because it's easier to read:

I ordered two teas during breakfast.

this is correct:

I ordered 10,500 packets of tea from a wholesaler.,

because this is harder to read:

I ordered ten thousand five hundred packets of tea from a wholesaler.