Learn English – “Don’t take the water, it is …” after touching the bottle with the mouth when I’m ill

I think wait or wait a minute is okay, and would sound softer, more polite, if you followed either expression with please; however, you also need to follow it up with an expression like I didn't (quite) understand that, or I didn't (quite) understand what you said; I didn't (quite) get that or I didn't (quite) get what you said. All of the preceding expressions could be preceded by Excuse me? and, in fact, when speaking to native English speakers, Excuse me is often sufficient on its own to communicate your intended meaning. Alternate, more casual expressions--which should also be followed by the same kind of explanatory follow-up statement to make your intended meaning completely clear--are: hang on, hang on a second, hold on, or hold on a second.

Sometimes a picture is worth a thousand words.

If I was training my daughter in the etiquette of sharing water from the same bottle, I'd probably say something along the lines of:

Pour the water into your mouth, like this –

and at this point, I would demonstrate, and then I would elaborate with a clarifying remark, such as:

– and don't let the bottle touch your lips

or:

– and don't put your mouth on the bottle

This method has two advantages:

• first, it shows her visually what you are trying to do,
• second, if she messes up and spills the water, or puts her mouth on the bottle, you've already had your sip :^)

Incidentally, this takes some skill. It might be best to exercise some foresight and have the child practice the technique at home. Until the skill is mastered, you can simply give the bottle to your child last and let her drink the remainder in the normal way. (But this is not parenting.SE; I'm digressing now.)