I am making up a bottle for you

Question

When you are preparing baby formula to your baby. Can we say,

Just wait a minute, I am making up a bottle for you.

For coffee, we say make a cup of coffee.

How about formula milk, what vocabulary to say you are making the milk?

Answer 1

Your sentence is not correct, mostly due to the broad use of the term "making up". The best change would be to drop 'up':

Just wait a minute, I am making a bottle

It is important to understand that although you are not making the milk itself, it is implied that you are preparing the bottle.

Answer 2

Making up isn't right. That's the kind of thing you would do when someone asks you a question to which you don't know the answer — you make up an answer. (Besides fabricating something from nothing, some other less relevant meanings of make up include applying cosmetics, taking an exam after everyone else took it on the scheduled date, and reconciling after an argument.)

Making a bottle could work. Preparing a bottle would be even better.

Making the milk wouldn't be quite right, though. That's a process that happens in the mother's mammary glands.