I did a similar thread a few months ago and someone suggested a sonic repeller which I haven’t resorted to yet.
If you know which way they travel to get in you could try these (non harmful) plastic spikes from amazon but obviously it can’t go over the whole lawn. you can get some that you can attach to the top of your fence if you have one.
I’ve also got the get off gel. I know it doesn’t work for everyone but it seems to have worked in masking their scent.
When I pick up the poo, I also sprinkle chilli powder on the area to mask their smell.
I’ve also sprinkled spikey leaves and twigs around so make it an inhospitable environment!
The water thing sounds good too, and if you know what time they come over, you could get a super soaker and spray them yourself.
Honestly there’s so much advice online but it is really trial and error with working out what that cat doesn’t like. It’s an ongoing battle for me too!