Orbs
These balls can be found in almost any floral department and aren't that expensive. Florist use them in vases and, when soaked in water, they balls expand. Let your child play in them with spoons, measuring cups, bowls, strainers, etc. They are available in different colors, so I like to mix them together. This way the kids can sort them by color. You could put some in a container and practice estimating too. Preschoolers need plenty of time to explore and this activity allows them to use their large motor skills. While they play ask them how the water/orbs feel and help them come up with describing words. The best part about these orbs is that you can leave them out to dry, they shrink back to their original size, and you can reuse them again and again!