With National Smoothie Day on Friday, numerous brands including Planet Smoothie are offering enticing deals to get you through the door and hydrated on a range of unique flavors. Most US fast-food joints tend to run promotions throughout the year, but various National Days give them a chance to up the savings. Recent examples could be free cocktails with National Margarita Day or the cinemas that offered great deals for National Popcorn Day. Planet Smoothie is offering free drinksOn June 21, Planet Smoothie is one of the many brands and businesses to be offering deals and promotions for Nation…