Without "it", saying "I couldn't drink" means "I couldn't drink any liquid" (tea, water, cola, etc). That is not what you want to express. Why would some milk being hot cause you to be unable to drink tea?In the following sentence, is the object it necessary?
The milk was so hot that I couldn't drink [it].
I'd appreciate your help.
Like before, this "drank" could mean drinking anything, not only the hot water. This sentence does not express "I drank the water after it was cooler". Instead, express this idea this way:The water was too hot, so I drank 10 minutes later.
But why is "The restaurant provided free mineral water, so she filled the glass and drank" OK?
And why is "The water was too hot, so I drank 10 minutes later" not idiomatic? What's the crucial difference?
Most native speakers would say The milk was too hot to drink, so I let it cool down.Well, neither of them is particularly idiomatic, since they are what they are — unnaturally fabricated statements that don’t reflect natural speech, or indeed typical conversational comments.
What did she fill the glass with? What did she drink?The restaurant provided free mineral water, so she filled the glass and drank.
What did she fill the glass with? What did she drink?
Because they are all in the same sentence, most readers will assume that she used "free mineral water provided by the restaurant" to fill the glass and then to drink. If you are not sure that readers will assume that, add "with it" after "the glass".