The cosmic-ray experiment AMS-02 has reported the possible detection of ~10 anti-helium events. Conventional production mechanisms struggle to explain the similar fluxes observed for both isotopes antiHe-4 and antiHe-3. In this talk, I discuss how these species could be created through nucleosynthesis occurring in fireballs of standard model (SM) antiquarks, leptons, and photons expanding with a
relativistic bulk velocity. Such events may be initiated by collisions between heavy composite states in the dark sector that carry negative baryon number. Since the fireballs are thermalized, this mechanism has the distinction of being agnostic to the specific dark matter model employed. It has the additional advantage of naturally producing antinuclei travelling at gamma~10, as observed.