The 22-year-old singer dodged and answered questions during a game of "Spill Your Guts or Fill Your Guts" on the CBS late-night-show.
"Camila, obviously, number one. That's for sure. Justin and Taylor? They're so close you're splitting hairs," Mendes said. "You can't even answer."
Mendes took a big bite of pork jelly and then jokingly chided host James Corden for having him play the game.
"You know how sick you guys are? You shipped this to me. You refrigerated it and shipped it to me across America. That's how sick you guys are," Mendes said.
For his second question, Mendes took a bite of scorpion dusted plantains rather than name the most amount of money he's been offered for an endorsement and who it was from. Mendes said Armani but declined to say the amount.
For his third and final question, Mendes avoided eating a cow tongue by reading his last five texts from Cabello out loud. In the texts, the couple discussed Mendes' appearance on The Late Late Show.
"She said, 'Is it disgusting? How's it going? Ew. LOL.' I said, 'LOL, the interview was awesome but now I'm about to eat some gross stuff," Mendes said.
Mendes and Cabello released a new song together, the holiday song "The Christmas Song," last week. The couple shared a music video for the song Tuesday featuring home movie-style footage of themselves at home.