Remove all items from the vinyl under-sink cabinets. Spray the inside of the cabinets with an all-purpose cleaning spray. Wipe it down with paper towels.
Measure the length and width of the bottom of the vinyl cabinets. Write down the measurements.
Cut a rubber mat, such as one used to line bathtubs or the floors of automobiles, to the measured dimensions. Place the rubber mat at the bottom of the vinyl cabinet.
Purchase an under-the-sink shelf that goes around your sink pipes and is made of plastic so it won't scratch the interior of the vinyl cabinet. These types of shelves not only give you a place to store items but also give you more protection from leaks, as any dripping water will leak first onto the shelves and not the cabinetry. It also protects cabinets from leaking products.