Put down paper towels or a similar material to bring up the liquid. Remove all of the urine from the floor as quickly as possible. If the urine has dried on the floor, such as might happen if a cat were to pee on the floor while the family was out of the house, get the paper towel wet and remove as much of the dried urine as possible.
Mix three parts water and one part vinegar. Put the mixture onto the spot and allow it to sit for a few minutes. Wipe it up with some clean paper towels.
Sprinkle baking soda over the urine spot. Allow the baking soda to sit. Baking soda is a natural deodorizer. Dip the scrub brush in water and gently scrub the spot with the baking soda. This will remove any remaining urine from the plywood and work the baking soda over the area for better odor removal.
Wipe away the excess baking soda and water with a damp soft cloth.