Sydney Sweeney is a new kind of Hollywood shapeshifter Clockwise from bottom left: Sydney Sweeney in "Euphoria," "Reality," and "Immaculate." Monica Schipper/Getty Images; HBO; Neon; Tyler Le/BI Sydney Sweeney is back in the public eye thanks to her role as Cassie in HBO's hit show "Euphoria." Sweeney deliberately markets herself as a blank canvas for brands and casting directors. This has made Sweeney a polarizing figure, but it's also allowed her to build a versatile résumé. In the second episode of "Euphoria" season three, Sydney Sweeney lounges poolside in skin-tight pants and a Barbie-pink crop top, eyes bugging out of her skull. She's in character as the beautiful and desperate Cassie Howard, trying to convince her best-friend-turned-romantic-rival, Maddy Perez (Alexa Demie), to propel her to internet stardom. "I just feel like if more people knew me, I would be huge," Cassie proclaims with childlike pride.…