So, the TVTropes page states him to be Ambiguously Bi, as he is confirmed to have a female love interest (Squilvia) but not confirmed to have any male love interests explicitly stated. However, though I haven’t seen the Sandy Cheeks movie, there is an instance, apparently, of him finding Sandy’s brother Randy so attractive that he faints. A Sexypedia article claims that as of “Saving Bikini Bottom: A Sandy Cheeks Movie, Squidward is canonically bisexual, as he is seen openly simping for fellow Sexyman Randy Cheeks. Squidward’s bisexuality should not come as a surprise to most fans of the show, or anyone who has seen certain theories regarding him.”