I had the same problem with wild cats living on my street . I tried a lot of things including planting things like lavender , all sorts of sprays. The only think that worked was this https://www.amazon.com/Good-Cook-12-inch-Bamboo-Skewers/dp/B0028LRKJI/ref=sr_1_3?crid=2L1UYJIPI1O7C&keywords=bamboo+skewer&qid=1681045535&sprefix=bamboo+skewer%2Caps%2C190&sr=8-3 .

I just put them in all the places they they liked to use as a litter. One next to each other . It doesn't look good but it worked. It became really difficult for them to use my garden as a litter box and after a few weeks they gave up and found another place . I took them out and they haven't back for a few years .