What smell of Febreze do cats like

Fragrance plug for home (cat-friendly)?

But cats do not have a strong odor, at least not in a way that the whole house / apartment smells of it.

Maybe it just smells every now and then? Is it extremely noticeable when you come home after a long absence (even without cats in).

If it is not because of the litter (expensive is not always good and odor-binding. If the legacies are not completely solid, litter is no longer helpful.) And not on the apartment, but "really" on your cats, then maybe there is also a disease behind it?
I definitely don't want to scare you! Sick cats (kidney problems, etc.) change their smell and this can also intensify.

And about these scented sticks: For the sake of the cats, I would do without them. In addition, it is terribly unpleasant to smell this artificial scent all the time, headaches are inevitable.

Better clean your apartment again thoroughly (at this time of the year you don't ventilate as often) and your radiators too! Sometimes there is dust, hair and other stuff in it that can also smell strange when heating.