Plain water is not recommended as it's best to use soft water, which means saline solution. You can achieve this easily by adding good Sea Salt to the water, 1 tsp per quart of water. Make sure it's an unrefined Sea Salt such as Celtic Sea Salt , available at health food stores.
You can also add to this solution a couple tablespoons of liquid Bentonite clay or chlorophyll or live acidophilus. All will help with candida.