▼ “Yes… They’re sitting right on top of the cat deterrent.”

▼ “Cat-deterring spikes from the 100-yen store. My cat doesn’t seem to mind them.”
I'm not sure what effect sugar would have on a cat. Cats have "sweet blindness" and lack the ability to taste sweetness. Since they don't register sugary tastes, they are generally neutral towards sugar. I doubt it would be an effective deterrent. Besides that, it might attract ants or other pests.
Homemade Cat Deterrent Spray - Stop The Scratching and Accidents
When a cat enters the protected zone, the Sunbeam® Sensor Egg Automatic Cat Deterrent detects its presence and emits a burst of air. The sound that it creates startles the cat and natural instincts take over and causes the cat to leave the area. DIY cat deterrent! Stop your cat from urinating on or scratching household surfaces.Homemade Cat Deterrent Spray - Stop The Scratching and AccidentsThe deterrents that emit sound to scare cats away would be great, but will it hurt my dog?
An "electronic" cat deterrent sounds fearsome, but in fact these devices are completelyharmless to cats and other animals. They have the advantage that whereas powders & chemicals haveto be re-applied over and over, an electronic system will last for years. Deterring cats need not be expensive. There are plenty of do-it-yourself home remedies you can tryout - and now there is even a special plant for your garden or yard that will repel cats effectively. Most electronic deterrents work by emitting an ultrasonic alarm triggeredby a motion sensor. The key to it is that the sound is inaudible to humans, but cats, with their betterhearing, will be startled and frightened away by the sound. Although the sound the cat hears is an effectivedeterrent it is in fact harmless to both them and other animals.For over a hundred years a product called "renardine" has been used successfully as a catdeterrent on such places as golf greens, farms, small holdings, parks and playing fields. If you would prefer something more hi-tech but also harmless to cats and all other animals, then thereare a range of electronic cat repellents on the market that can do the job. As well as ultrasonic deterrentsthere are even electronic scarecrows available now that will target trespassing cats with a jet of water! Toms love to leavescent markings to let other cats know their territory. This smell is both offensive and lingering. Manytimes it will lead to more cats coming around - unless you have an effective cat deterrent! Deterring cats need not be expensive. There are plenty of do-it-yourself home remedies you can tryout - and now there is even a special plant for your garden or yard that will repel cats effectively. Cats are not keen on the smell of citrus either. So you could try using orange or lemon peel in youryard as a deterrent. Similarly some folks advocate coffee grounds, blood meal, cayenne pepper, lavenderoil, lemon grass oil, citronella oil, peppermint oil and eucalyptus oil.