It is implied a female hostage is required to have sex with any man in the gang who demanded it.
Women are seen bare breasted in nonsexual context. Several men are seen bare chested.
We see full frontal nudity from Patty as she lies in the bathtub. The SLA have sex with each other and discuss their various sexual practices from fornication to homosexuality to masturbation and put marriage down as outdated and bourgeois. Patty and her boyfriend appear to be cohabiting before Patty's abduction.