Sydney Sweeney turned HBO into the Hot Box Office Sunday night … ’cause “Euphoria” fans got an eyeful during the latest episode, when Cassie dove headfirst into the wild world of fetish content creation.

Take a look … the fifth episode of Season 3 showed Sydney’s character serving up one jaw-dropping look after another while filming spicy OnlyFans-style videos from her bedroom setup.

Cassie rocked a dangerously low-cut polka dot jumpsuit while skipping rope for the camera … then switched gears in a skintight police costume that left basically nothing to the imagination.

The scenes instantly sent fans spiraling online … with viewers calling the episode one of the show’s most unhinged — and thirstiest — yet.