Monster Donut

Monster Doughnut Shop was a chain of doughnut shops across the United States. It was somehow connected with the Hydra, as another Monster Doughnut shop popped up somewhere every time the Hydra grew another head (after losing one). It also seemed to be magic, as the shops grew out of thin air. Tyson thought that their doughnuts were exceptionally good. Most chain stores and restaurants, like Monster Doughnut, are connected to the life force of a Hydra (or another monster). This was stated by Annabeth as being the reason some stores pop up so fast. This trick was discovered by some children of Hermes in the 1950s.

The Sea of Monsters
After Percy, Annabeth and Tyson escaped the Princess Andromeda, they hid in an old hideout created in the days when Annabeth, Thalia, and Luke were on the run. Wanting some privacy with Annabeth, Percy told Tyson to go out and grab some donuts. They were surprised when he came back with a box of donuts, so they went and saw that there was a Monster Doughnut shop nearby. Apparently only monsters are able to purchase the donuts (which was the reason how Tyson was able to, since he was a monster)while demigods would be killed, and it appeared partly because Tyson wished it. A hydra appeared and when Percy cut off one of it's head, Annabeth told him that another Monster Doughnut shop had just appeared somewhere else in the country. They were eventually saved by Clarisse who used a cannon from the Confederate Ironclad battleship, CSS Birmingham, to slay the Hydra.