Obviously it would be treated by the police as some felony level chemical warfare. But with something as benign as cologne it has the potential to make such a response look excessive even to the brunch crowd. "It's just cologne" I can hear someone saying in the outdoor TGI Friday's seating area.
It's offensive smelling, sure. But it's not anywhere close to the same level as throwing other questionably smelling or gross liquids such as piss, blood, etc. And it's not even comparable to something like throwing milkshakes. No one buys a milkshake to put on themselves, but some people do buy cheap cologne to wear.
It's cheap and readily available to buy. Difficult to source/trace since it's so common.
From a physical irritant perspective it would just be miserable standing there in full riot gear with a headache due to buckets of cheap ass cologne being thrown on everyone around you. They can try and clean it but that shit sticks. It will go back to the station with them -- it will remain on their gear which the station likely won't pay to have cleaned. It will be in the vans that they all pile into. And it will go home with them.
Just a thought I had and thought it would be great to try in a video game or at the next gender reveal party.