Preheat oven to 350F°. Line 24 muffin tins with liners and set aside.
In the bowl of a mixer, beat cake mix, egg whites, and soda on low speed for 30 seconds. Scrape the sides of the bowl, then beat on medium speed for 2 minutes.
Fill prepared muffin tins 2/3 full and bake for about 15 minutes, until tops spring back when lightly touched in the center. Let cool completely on wire racks.
In a medium bowl, fold together Cool Whip Free and Jell-O powder.