Glubby Glubs induced a feeling of relaxation, as well as drowsiness and memory loss, because they stole energy from those who bought them and passed it to the seller. They were also capable of draining the energy from a TARDIS, as well as from Time Lords. (AUDIO: Retail Therapy)
They were sold by the Glubby Glub company for 5 pounds each to sellers, who sold them to others. The most successful sellers were called Go-Getters. Jackie Tyler managed to become the top Go-Getter, partly due to the influx of energy from the Doctor's TARDIS. Many celebrities used Glubby Glubs to preserve or improve their looks.
The Ninth Doctor, with Jackie's help, took control of the body of the head of the company producing them and sent the energy back to the victims, causing him to rapidly age and die and deactivating the Glubby Glubs. Before returning to his own body, the Doctor also induced the former customers and sellers to forget about what had happened, ending the fad. (AUDIO: Retail Therapy)