When I drink water, there are two ways to drink. Either I can touch my mouth to the bottle or keep the bottle away from my mouth.
Suppose my friend comes and asks me for water. As I am suffering from fever, I want to say to him: "Don't take my water, it is …". What should I fill there?
I was thinking to use "used" there. But "used" can be used in the case when I didn't touch water with my mouth. So, what should I use? I am not getting the proper word for it.
"Contaminated" is a common term used to describe something that has been in contact with dangerous organisms or substances and would pass them on. It is most likely what you are after.
"Tainted" is also used in this case, but is less formal and slightly less precise (it could be tainted with something distasteful, but not harmful).
"Adulterated" is the term used in technical and legal communication (FDA reports).
To answer your second question (comment), I do not think there is a single specific word in English to describe "risky-because-of-having-been-drunk-out-of". You would have to say, as snailplane suggests, "I drank out of that". The fact that you touched the water would be implied, because you wouldn't warn them if you had not.
As a native speaker, I wonder: is the problem with the water, or with the bottle?
That said, a few expressions come to mind. The first one is the most direct:
You might not want to drink from that bottle; Ann already had her mouth on it.
The second is more of a euphemism than a scientific fact:
Don't drink from that bottle – it has germs.
(We don't know for a fact that the water has any contaminants, but the word germs is often used to refer to unseen microorganisms that could spread disease, particularly in informal speech.)
Because the concern is mainly with someone else drinking from the bottle, you could also say:
Be careful! That may have someone's backwash in it.
TFD labels this definition of backwash as "informal", while the Urban Dictionary says:
Backwash is often created inadvertently or unintentionally when liquid escapes the mouth during the process of drinking .. When multiple people drink from the same container, there will usually be some amount of backwash put back into the container.
As a footnote, the adjective for drinkable water is potable, though anyone who would deem bottled water as non-potable simply because someone else drank from the bottle is probably using extreme hyperbole, or else is an overly sensative germaphobe.
To the best of my knowledge, there is no single English word that means "my lips have touched this drinking container". You would have to use a descriptive sentence or phrase, like "I drank from this" or "I had my lips on this" or, particularly if you had been sick, "This has my germs on it", etc.
