If you want to make painting with acrylic color, you need to have water with all necessary things as it dries out instantly and your brush may spoil. So to protect your brush you need to have water near the pallete so that the brush can be kept inside water. You also need a water sprayer to spray on the paint to stop them from drying out easily. You need to have little soapy water so that the brush can be cleaned after the job is finished. Otherwise the brush can be destroyed.
Source: http://myartmagazine.com/acrylic-paintings?page=1