Fill a large saucepan or teakettle with cold tap water. Bring the water to the boil over high heat.
Place the Rival crockpot in the sink or on a flat, steady surface like a counter or table. Pour 1/4 cup white vinegar into the bottom of the crockpot.
Pour as much of the boiling water into the crockpot as it will hold without overflowing. Stir the water and vinegar mixture with a wooden spoon and place the top on the crockpot. Allow it to rest for one hour or until the water is cool.
Pour the water out of the bottom of the crockpot and rinse it with warm tap water. Wash the inside with a soft, nonabrasive sponge and very mild dish soap.
Repeat the process if food remains on the inside, allowing the water and vinegar mixture to rest until cool once more.
Dry the inside with a clean kitchen towel before storing it for later use.