Soaking dry food in water to “moisten” it is not a good idea. Dry food, when moistened, is essentially transformed into bacterial soup. The bacteria load can be extremely high in dry food and once you add water to the mix, you’ve created an ideal environment for fungi and bacteria to multiply.
When you moisten dry food, for example, you create conditions to quickly grow fungi in the food. The result is vomitoxin, aflatoxin, and mycotoxin production. Vomitoxin is a toxic substance produced by mold that can (and has) contaminated wheat used in dry pet foods resulting in serious illness and even death.
If you want moisture in your cat’s food, (which you very much should want because it’s best for your cat, better to feed a truly high-quality canned food or (still better in my view), make your own cat food.
If you are feeding dry food—it should be kept refrigerated. But really, you shouldn’t feed dry food. You and your cat can do so much better than that.