Efron, wearing in a T-shirt, jeans and a baseball cap, joined a dressed-up Burke and the group in the back VIP room, where they went seemingly unnoticed by fellow club-goers.
“At one point, they went up to get drinks from the bar, and they showed off their dance moves,” an onlooker tells PEOPLE. “They ordered a few cocktails to bring back for them and their friends.”
Efron, who took care of the tab, had his hands full with the beverages so Burke stepped in and signed the receipt for him.
Continuing to chat throughout the night, the insider says Buke and Efron were “definitely flirty friends and didn’t talk to many other people.”