Squirrels object to capsaicin, cider vinegar, mothballs, urine of predatory animals and skunk-like smells. These items can be used to deter squirrels from both the indoors and outdoors.
Sprinkle hot pepper flakes, white or black pepper, hot sauce, chili powder or garlic amid plants and in other areas to repel squirrels. Hot pepper products also work well for deterring squirrels away from bird feeders, because the birds are not sensitive to the capsaicin.
To deter squirrels with cider vinegar, place apple cider vinegar-soaked cloths around the area. Mothballs are particularly useful for deterring squirrels away from inside the home. Various stores sell squirrel deterrents that produce a scent similar to the urine of squirrel predators. For appropriate outdoor areas, planting the Fritilliaria imperialis plant can repel squirrels since it smells similar to a skunk.