The Bad Beginning
The series begins when Sunny, at Briny Beach with Klaus and Violet, notices Arthur Poe, a friend of the children, moving towards them. He informs the children that their parents have died in a terrible fire, which has also destroyed their home. The children, now orphans, are sent to live with the evil Count Olaf, who abuses them and attempts to get the fortune that their parents left behind by marrying Violet. At the time, Sunny is dangling from a cage on top of a very high tower. At the end she is rescued and Count Olaf's plans are ruined by Violet, and Mr. Poe has to find another home for them, and it happens to be one with Uncle Monty.
The Reptile Room
Sunny and her siblings are sent to live with Uncle Monty, after the events of The Bad Beginning. Sunny befriends the Incredibly Deadly Viper, Uncle Monty's latest discovery, a completely harmless snake. She later stalls some time with the viper so that Violet and Klaus have a chance to find clues that would prove that Uncle Monty's lab assistant is really Count Olaf. Sunny also bites Dr. Lucafont's hand and it cracks, revealing that he is the hook handed man. Sunny, Klaus, and Violet move on to their next guardian, Aunt Josephine.
The Wide Window
Sunny and her siblings move in with Aunt Josephine, another distant relative. She receives only a rattle here so she trades with her other siblings and gets a Pretty Penny doll. She has allergies for the first time in this book after eating a peppermint. She grew hives (which is what Violet suffers when eating peppermints) and had a swollen tongue (which Klaus suffers when eating peppermints). She also manages to steal a sailboat from the Enormous Androgynous Person who guards Captain Sham's Sailboat Rentals. Sunny also is a tiller mover here. Towards the end of the book, she bites Captain Sham's fake peg leg to prove that he is really Count Olaf.
The Miserable Mill
Sunny and her siblings are then sent to work at Lucky Smells Lumbermill, Paltryville. The workers at the lumbermill only get gum for lunch so Sunny bites pieces of wood, pretending that they are apples, carrots or cheese enchiladas. She also battles Dr. Orwell here, using her four sharp teeth against Dr. Orwell's cane sword.
The Austere Academy
The Baudelaire orphans are then sent to the boarding school, Prufrock Preparatory. Sunny gets hired as Vice Principal Nero's secretary, while Violet and Klaus are students (since babies aren't allowed to be students). She does all the stapling and typing for him. She is forced by Nero to make staples out of long metal rods when his staple supply runs out. Thankfully, she manages to steal some of them so that her siblings (namely Violet) can make staples out of them. She also experiences S.O.R.E. (Special Orphan Running Exercises).
The Ersatz Elevator
Sunny lives in the penthouse of the Squalors where she and her siblings find the two Quagmire triplets. She also is brave enough to climb an elevator shaft with her teeth when Esme pushed them down one. She also joins an auction and said that she would pay a thousand for V.F.D. (Very Fancy Doilies).
The Vile Village
This time the children get to pick where they go, and they choose to go to V.F.D. (believing it might help in discovering the Quagmire triplets message), but it turns out to be the Village of Fowl Devotees. Sunny gets accused of murdering Jacques Snicket and that her siblings are her accomplices in doing this crime. She also thought that the Quagmires could be near, so one night, she stayed under Nevermore Tree and found out that crows were sending Isadora Quagmire's couplets.
The Hostile Hospital
Sunny, Klaus, and Violet have to make sure that are not recognized in the book The Hostile Hospital, because they are being accused of murder. Sunny disguises as one of the white faced women. She pokes the hole in the alphabet soup can that Violet uses for her invention. Klaus and Sunny rescue Violet from having her head cut off by Count Olaf and his assistants.
The Carnivorous Carnival
Sunny disguises as Chabo, a half baby, half wolf freak and she works for Madame Lulu in the Caligari Carnival. Sunny's talent for cooking is also discovered here. She places a bit of cinnamon to the hot chocolate, which caused the hot chocolate to taste better (Hugo thought it was some kind of wolf recipe.). She is also captured by Count Olaf because Madame Lulu betrayed them.
The Slippery Slope
Sunny worries about Klaus and Violet and how they survive while she is forced to work for Count Olaf. Olaf forces her to do chores for him like cooking and setting up a tent. She states that she is not a baby anymore when Violet calls her a baby. She now improved in cooking, making lox and delicious False Spring Rolls. Sunny's brother and sister managed to rescue her and she manages to know that the Snicket File (except for page 13) is now with Count Olaf and that the last safe place was the Hotel Denouement.
The Grim Grotto
Sunny rolls up in a diving helmet and it gets poisoned by a mushroom while they traveled into the Grim Grotto. She gets sick and nearly dies. She managed to create a birthday party for Violet (with Phil's help). Sunny makes a coconut cake. She also knows that wasabi is a counterpart of horseradish which removes the poison from her body. When the Queequeg gets a leak, Sunny covers it using gum.
The Penultimate Peril
Sunny, along with Klaus and Violet, gets assigned to be a concierge at the Hotel Denouement. She hears about Mr. Remora's, Mrs. Bass's and Vice Principal Nero's talking about the party. She also tries to stop Olaf killing Dewey (but fails). Sunny helps start the fire in the hotel, and Count Olaf is proud of her for it. To escape the fire her and her siblings, along with Olaf, take the boat that Carmelita Spats had on top of the hotel (in the swimming pool).
Sunny, Violet, and Klaus are stuck on a big ship with Count Olaf, fleeing from the burning Hotel Denouement. After a huge storm, Sunny and her brother and sister find themselves on a coastal shelf of an island. A little girl named Friday Caliban gives them a tour and introduces them to everyone. She gives Sunny a whisk because she knows Sunny liked to cook food. A few days later, Sunny, Klaus, and Violet are abandoned on the coastal shelf with Count Olaf. They find the pregnant and weak Kit Snicket on top of a raft of books. Sunny sadly tells her that her husband Dewey Denouement is dead. Towards the end of the book, Kit and Olaf, who are dying from the Medusoid Mycelium poisoning, recite a short poem called The Night has a Thousand Eyes together. It is unknown whether this poem is part of V.F.D. or not. Then Count Olaf dies. A few moments later, Kit's baby is born, and Kit dies. Sunny adopts little Beatrice along with Klaus and Violet. The four of them leave the island a year later.
After The End
Though the fate of Violet is ambiguous, Sunny's fate is more well known: several sources state that something happened to The Beatrice - it sank on some sharp rocks when they were close to the mainline, though what made it hit the rocks is unknown - and Violet was forced to make an "emergency repair" to it, which allowed the ship to land, successfully, on the mainland, allowing at least Violet and Sunny to survive.
While Violet may have died some time after the Beatrice docked (she is stated as returning to Briny Beach for a third time, but her fate after that is unknown), Sunny, at least, survived to be "a young woman" who often discussed her new cooking recipes on the radio.
However, despite all his research and hard work, even Lemony does not know the current position, location and status of the Baudelaire children, implying that Sunny has gone into hiding or is using a fake name on the radio.