On this week’s Modern Retail Rundown: PepsiCo-owned Gatorade is adding more hydration SKUs that resemble Liquid I.V. and Prime. Meanwhile, department store retailers face yet another hurdle: A new law that limits payment late fees can hurt credit card revenue for retailers like Macy's and Kohl's. Lastly, Bark just announced Bark Air, a new airline program that offers pets and their owners a more comfortable flying experience.