Ok, so, whatever it's used for shouldn't change what it is. Whether used to spray perfume, or squirt oil or grease or whatever substance, the item must surely be a hydraulic gun. Could be used for liquids of various viscosity, whether, water, perfume, grease or something else If that's not correct, I'm stumped.
It is not a hydraulic gun, it works with a piston pump. What something is used for, very definitely defines what it is, unless it is a multi-use item. You would not use this for something as thick as oil because it would not work with the spray function. You would not use it with perfume because just one spray would use way too much. You did mention water as one of your listed liquids but not as an actual guess, that would have been correct. It is a water spritzer bottle, generally used for misting houseplants. I would have accepted any answers that could have worked with it but, as stated, oil and perfume would not. Spray bottle would have been an acceptable answer though. The actual object