Epiphanius says the borborites were inspired by Sethianism, and had as a distinct feature of their rituals elements of sexual sacramentalism, including homosexual intercourse, smearing of hands with menstrual blood and semen, and consumption of the same as a variant of eucharist. They were also said to extract fetuses from pregnant women and consume them, particularly if the women accidentally became pregnant during related sexual rituals.
As all these tellings about the borborites come from their opponents, we don't know for sure if they are true or exaggerated. S. Gero finds them plausible and connected with earlier Gnostic myths, as he writes in With Walter Bauer on the Tigris: Encratite Orthodoxy and Libertine Heresy in Syro-Mesopotamian Christianity, one of a collection of works published in Nag Hammadi, Gnosticism, and Early Christianity in 1986.