Brief Answer:
You can have water or fruit juices.

Detailed Answer:
Hello dear, welcome to Ask a doctor's service.
I read your query and here is my advice.

Of course you can drink water after putting nebulizer.
Sometimes using nebulizer may cause dryness of the mouth and having water will help you with it.
Also you can use lemon candies to keep mouth hydrated.
You can have a drink if you feel weak after using nebulizer like fruit juices.

Hope I have answered the question.
Let me know if I can assist you further.

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