Sydney Sweeney Stuns in Steamy 'Euphoria' Fantasy Scenes

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.