The phrase "one's warm water" means the things or activities that make someone feel comfortable or content. It refers to a personal preference or something that brings joy and relaxation to an individual. Full definition
To begin, place 1 1/2 cups of warm water in a mixing bowl, with 1 tablespoon of brown sugar and 2 teaspoons of kosher salt. (cosmopolitancornbread.com)
Surface wash in warm water with mild soap and rinse thoroughly. (diaperjunction.com)
Combine the miso with 1/4 cup warm water in a small container and whisk until smooth. (vegkitchen.com)