Q: My one friend swears the fast breaks when you inhale cologne. The other says no. Who is the correct? Also can fragrances be used in cars and bathroom affect the fast? Cologne on body? clothing?
A: Perfume itself would not negate fast.

Inhaling cologne intentionally would negate fast.

Merely placing it upon the body/clothing would not break your fast, so long as you do not inhale it directly prior to placing it on your body/clothing.

Same rule would apply for using incense in the homes, bathrooms and cars.

Intentionally sniffing perfume would only call for that given fast to be made up.

Allah Certainly Knows Best.