HI - I have 3 cats and although I wouldn't discourage them from my garden I understand that others do not want them in theirs. I don't think vinegar will do your garden much harm, but may make some areas too acidic so be carefull...and you would probably need a lot to make an difference. My cats hate nail varnish...why not try paiiting something with nail varnish to distract them??? Another deterrent could be ground coffee, so when you've done with your cafetiere throw the coffee on the garden - I believe slugs and snails hate that too!!

I use dilute vinegar around my Blueberries but it can easily kill non-acid loving plants and I doubt it scares off cats. Garlic perhaps would and that also discourages slugs. The only way I found to keep cats away is sticks/netting on areas where they poop and scratch the soil.

Neither garlic nor coffee grounds will actually deter a determined cat. Sticks, netting or really sharp grit work.

the nail varnish as a deterrent only works while there are vapours coming from it. once dry there isnt any point.

the neighbours cats seem to like the coffee grounds so I just compost it now.

The only vegetables that benefit from vinegar are zucchini in a glass jar! Otherwise I would choose to avoid it.

I had/have a similar problem - I do have cats too but what I found was when I managed to deter them from where they were fouling - by putting up turned flower pots on canes in the gaps between plants - they moved elsewhere in the garden. Personally I just accepted that they were going to use a specific area and live with it. Lucky for me it's in a far corner under a hedge and I just need to remember what I may come across when I'm in that area.