Vinegar is the main ingredient of most bitter-apple sprays. The tart flavor makes most dogs grimace and will deter them from nibbling your valuables. If the scent of the vinegar bothers you as much as it does your dog, you can also use lemon juice.

The problem with vinegar and lemon juice is exactly what you might imagine. Some dogs may actually like the way it tastes! If that's the case, use both vinegar and lemon juice, or try a pickling spice called "alum" or good, old-fashioned yellow-flavored mouthwash (you know, the really gross stuff). You can also try a pinch of cayenne pepper in the mix, but be careful, as it may stain some surfaces.

Pour the ingredients into a 24-ounce spray bottle.
Shake vigorously.
Test the spray in an inconspicuous spot on your furniture, shoes or other items before spraying it all over.
Reapply as needed.