Jason Kelly is a lawyer who works for his father. Jason's grandmother dies, and after the funeral, his Army veteran grandfather, Lt. Colonel Dick Kelly, asks Jason to drive him to Boca Raton, Florida due to his drivers license being suspended. Jason is marrying his controlling fiancée, Meredith, in one week, but decides to take his grandfather anyway.
On the way there, the two meet Jason's old photography classmate, Shadia, along with her friends Lenore and Bradley. Dick and Lenore are instantly attracted to each other. Dick tells the girls that he is a professor and that Jason is a photographer. They all go their separate ways, but Dick convinces Jason that they should meet the girls at Daytona Beach, Florida, because Dick wants to have sex with Lenore. The two go to a golf course, where Dick flirts with two women.
At Daytona Beach, they meet up with the girls and the girls' friends, Cody and Brah, with whom they compete in beer chugging. That night, a drunk Jason, wearing nothing but a Hornet fanny pack, parties and is tricked into smoking crack cocaine by a drug dealer named Pam. He steals a motorcycle and wakes up the next day on the beach. During an awkward FaceTime session with Meredith, a toddler grabs the fanny pack and takes it off; the boy's father suspects Jason of being a child molester and calls the police, who promptly arrest Jason. Dick bails him out, and the two visit Dick's old Army friend Stinky in a nursing home. They meet the girls again and enter a flexing contest with Cody and Brah; when they lose, Dick alters a T-shirt cannon to fire a beer can at the winning duo, hospitalizing them. With Cody and Brah in the hospital, Jason and Dick take their hotel room. After Dick reveals to Jason that he was a Green Beret, the two go to a nightclub with the girls. Dick gets into a fight with some men after they bully Bradley for his homosexuality. The next day, Jason goes to a protest with Shadia and she tells him that she is leaving soon and going to live on a ship for a year.
That night, Jason plans on telling Shadia who he really is, but before he can, Cody does an online search using information he saw on Dick's (still valid) driving license, and tells Shadia that Jason is already engaged. Jason then gets caught with drugs which were planted by Cody and Brah, and is thrown into jail again. The next day, Dick bails him out and tells Jason that his real reason for the trip was to convince Jason not to go through with the wedding. A disgusted and furious Jason leaves Dick and drives back home.
During his wedding rehearsal, Dick hacks into the computer system, revealing embarrassing photos of Jason during the party. Jason says that he cannot marry Meredith, who reveals that she had an affair with his cousin, though Jason does not hear this information due to poor acoustics, his cousin instead quickly telling him that Meredith has told him to do what he wants to do. He, Dick, and Pam, with David (Dick's son and Jason's father), use Pam's ice cream truck to catch up with the bus that Shadia is on as she is leaving. Jason and Shadia kiss, and he gets on the bus with her, while David and Dick, previously estranged, reconnect. Dick goes to his house in Boca Raton and finds Lenore there waiting for him, and they have sex. Dick and Lenore get married and have a baby boy, and Jason and Shadia are named the godparents.
Robert De Niro as Lieutenant Colonel Richard "Dick" Kelly,
Zac Efron as Jason Kelly,
Zoey Deutch as Shadia,
Aubrey Plaza as Lenore,
Julianne Hough as Meredith Goldstein,
Dermot Mulroney as David Kelly,
Jason Mantzoukas as Pam
Jeffrey Bowyer-Chapman as Bradley,
Jake Picking as Cody
Michael Hudson as Brah
Adam Pally as Nick
Henry Zebrowski as Officer Gary Reiter
Mo Collins as Officer Jean Finch
Danny Glover as Stinky,
Brandon Mychal Smith as Tyrone
Eugenia Kuzmina as Hippie Cathy,