My cat was like this. I thought it was just the central heating making her moult more. She was sick three times a week.
But I took her to the vet with a urine sample and it turned out she had a uti and it was making her feel crap so she was making herself sick to try and make herself feel better. I had no idea.
Id ask the vet for a urine sample container. Or see if your pharmacy could give you one (white top not red top as it has to be empty and not have people urine preserving crystals in it!! )
The way you get a at urine sample is to buy special plastic cat litter than doesnt absorb pee called KatKor (other brands are available), clean the tray thoroughly and put this stuff in and wait til she pees.
Then after she goes as it’s all sloshing round the tray and you can suck it up into a small pipette or syringe or pour it into a sample container. Just keep an eye on her to try and get it as soon as you can so it’s not lying all day.
Or wait till she starts to pee and if there is room put a small container (I use a baking scoop from Ikea 50p or somethimg as it had a handle to reach under her tail end) into the urine stream and take a few scoops.
Keep it in the fridge if you cannot get to the vet immediately but try the same day, sooner the better. My vet lets me hand in a sample whoever and phones with results and a link to pay. The do a dipstick it and look under a microscope as sometimes infections dont show up with a dipstick.
Ive got her on antibiotics and only once furball in 7 days, which seems about right for her.
uti and kidney probs are very common in cats. The fact yours is drinking more sounds like thats what it could be so I’d get kitty checked out. Even if you hand in the sample with a view to bringing the cat in later if anything shows up.
The dipstick / microscope check can be between a tenner and thirty quid depending on where you are.