You are fasting

From this hadith scholars say that if a person is fasting he must not exaggerate in

Sniffing the water of his nostrils. Why?

because the passage from the nostrils goes directly to the stomach, so

You may drink water and you may sniff it and it would lead to the same passage to your stomach

And this is why scholars say that

if you put nose drops and

You find the taste in your throat

This breaks your fasting

But if you put eye drops

ear drops if you swim

this has no impact on your fasting even if you find the taste of ear drops or

eyedrops in your throat

Because this is not a normal passage to the stomach

But the nose is so using nasal drops

If you find the taste in your throat, or you lead it leads you to swallow some of it this

nullifies your fasting