I love using buttons with kids and you will see them come up in many activities I do. They are just so fun, colorful, you can find different shapes– there is just so much you can do with them (and they are pretty cheap-BONUS!). I also love doing activities in plastic bags because it gives the kids a different sensory experience! This activity also helps with fine motor and my kids loved it. I left it out on the table and they kept coming back to do it again.
If you don’t have buttons you could also do this activity with coins and sort them by amount–anything flat works best. I just took the back of a recycled cereal box, colored some jars on the front and put the buttons in the bottom of the bag. My kids slid them into the correct jar–you could also put numbers on the jars so you have multiple activities– Sorting by color and one-to-one correspondence!