"To the man who has showed me more beautiful places in this past year than I have ever seen in my whole life. Happy birthday, Cole. Thank you for all of the adventures and here's to many more ?," the actress wrote on Instagram, alongside a snap of Sprouse surrounded by greenery and skyscrapers in the distance.
K.J. Apa also took to Instagram to share a pic of Sprouse, writing, "One for the books. Ps happy b day love ya heaps bro."
Meanwhile, Madelaine Petsch and Casey Cott poked fun at their co-star by writing silly captions on their Instagram pics.
"The only day I'll let you get more attention than me... (who am I kidding that's everyday) happy birthday turd ?," Petsch wrote, while Cott captioned his pic, "Happy birthday. You're welcome for the followers."
ET spoke with the Riverdale cast at Comic-Con last month, where they dished on what to expect in season two, as well as teased new love interests for their characters. Find out who's pairing up in the video below!
Riverdale returns Wednesday, Oct. 11 at 8 p.m. ET/PT on The CW.