Smart drink ingredients often include substances such as DL-phenylalanine or L-phenylalanine, L-tyrosine, choline (trimethylaminoethanol), pyroglutamic acid, B vitamins, glucuronolactone, and DMAE (dimethylaminoethanol). These amino acids were claimed to have positive or enhanced effects on alertness, stress resistance and energy levels.
Some of the acids, then considered "foods" and nutritional supplements by government agencies like the US Food and Drug Administration (FDA), changed in status and have since been removed from store shelves. Others are still available  when  prescribed by a doctor.