Put a teaspoon of vinegar in your pet's water bowl to help prevent fleas. Some pets do not like the taste, so you may need to adjust the quantity of vinegar. You can use all-purpose vinegar or apple cider vinegar. If you have adjusted the amount and the pet still will not drink, then you can buy vinegar in capsule form. Fleas will be repelled by the smell radiating from your pet's skin. The remedy also acts as a natural deodorizer and boosts an animal's immune system.