Tonka is a weirdo.
We use two water bowls. One is one of those big plastic bowls you see in Chinese restaurants, and the other is a slightly smaller stainless steel mixing bowl. One or the other is net to Tonka’s water dish. They are replenished from the kitchen faucet. But Tonka likes to drink outside. See, the other bowl stays on the deck. If it’s not there, Tonka will lick rain water off of the deck, or find some other source. It doesn’t matter which bowl is out there; he’ll drink out of it. Inside, he only drinks out of the bowl if we’re not letting him outside. Same water, which we keep fresh, same dishes, and yet he’ll go without drinking until we let him outside.
Did I mention he’s a weirdo?
Cats like running water when they can get it. Perhaps the wind blows across the bowl outside enough to simulate this for Tonka. Or at least, more than the inside bowl. You could look into getting one of those bowls with a pump to circulate the water for inside. Our vet recommended getting one for Noir Kitty so he’d drink more water to ease his occasional constipation.
Edited to add: But, yeah, cats are weird.
I recently read that cats do not like to drink water near where they eat. The idea being that, in the wild, they are eating dead animals and the water nearby may be contaminated. So, try moving the indoor water bowl to another area and see if that solves the problem. And also that cats like to drink from flowing water sources.
Yep, if I turn the faucet on here come the cats. They drink from a bowl usually the dogs bowl. I keep one in laundry room too, that is the hangout place. But they love the faucet. My male is trying to figure out how to turn it on himself. It’s a stiff faucet so I believe he won’t succeed, he’s fooled me before though.
Of course cats are weird; they’re cats.
I’ve got one - ironically with kidney issues - who will not drink still water, so I have a large fountain dish that she will only just deign to stick her head in. (Come to think of it, this is also the cat who will literally starve herself if I have to change the sort of food I’m feeding my fuzzy beastbutts…she apparently fixates on something about it. Had a hell of a time getting her off discount store kibble and onto decent food when I got her. Not even honestly sure how I did it.)
Might be worth trying a fountain-type bowl for Tonka. I don’t recommend one of the ones with a refillable water reservoir - you’ll be refilling it constantly. One of the ones that’s just a recirculating pump in a bowl of water should do fine.
When you go to a restaurant, don’t you sometimes enjoy having a drink out the terrace rather than inside? So does Tonka.
Also seconding or thirding the water fountain recommendation. It’s both more pleasant for them and healthier.