I just use my breath to blow forcefully at the cat's face. Only works at close range of course. Indeed I have a cat that never minded getting wet, so water sprays don't have any effect.
In Sweden 20°C is the lowest acceptable indoor temperature for apartments.
I lived at a place that had 17-19°C indoors for a while. Spent all my time nestled under triple blankets. Sitting still at those temps gets real cold after a while, unlike being outdoors where you're more likely to be moving (and maybe get some sunlight to warm you up, too).
With my cats the belly rub appreciation came with age. At 2 years old it was all playful teeth and claws, but after 8 years or so it is 100% belly rubs and cuddles.
The fluffed up fur on the back makes me think the cat might be in some pain/discomfort. We had a cat with FORL who had severe tooth pain, she often looked like that when she wasn't feeling well. Cats are really good at hiding pain so it took us a while to understand.
This cat might be just fine though, I don't know the context of the picture.