Spray insides of 2 large microwave-safe mugs with cooking spray. Whisk together Reddi-wip, Egg Beaters and cake mix in medium bowl. Place half of batter in each mug.
Microwave each mug individually on HIGH 1 minute to 1 minute 15 seconds or until set. Invert each cake onto plate. Top with caramel syrup and sprinkle with crushed pretzels. Serve immediately with additional Reddi-wip, if desired.