What you need:
and this worksheet (or make one of your own)
You may color in the worksheet yourself, or have your child do so, for more pattern practice.
Have your child match the patterns using the snap cubes. You can then take this activity a step forward by discussing AB patterns, and onto ABC patterns, etc. You can have them come up with their own patterns, and for the younger children (I have a just turned 2yo), they can have fun just exploring the cubes, and working on fine motor skills snapping and unsnapping them.
More items for practicing patterns: