The only enhancers I've seen at smoothie bars are different proteins, L-Glutamine, and I remember seeing one smoothie recipe at a gym where they added micronized creatine, ribose, and a couple of other things as a preworkout smoothie. It wasn't all that popular at that gym since alot of people were using SciTech and MuscleTech stuff and adding the powders to their carboforce drinks during the workouts.