Wikipedia summarizes the debate of what "Soma" and "Haoma" were and discussed their religious context:
There has been much speculation about the most likely identity of the original plant. Traditional accounts with unbroken continuity in India, from Ayurveda and Siddha medicine practitioners and Somayajna ritualists undoubtedly use "Somalata" (Sarcostemma acidum). Non-Indian researchers have proposed candidates including Amanita muscaria, Psilocybe cubensis, Peganum harmala and Ephedra sinica. According to recent philological and archaeological studies, and in addition, direct preparation instructions confirm in the Rig Vedic Hymns (Vedic period) Ancient Soma most likely consisted of Poppy, Phaedra/Ephedra (plant) and Cannabis....
Avestan, a.k.a. Zend, a.k.a. Northern Old Iranian, closely related to Old Persian, that is a sister language of Sanskrit) epics respectively.Materials found in two Tarim Basin cemeteries seem to support the leading hypothesis, of many serious proposals, that the ephedra is indeed an active ingredient in what is called "Soma" and "Haoma" in the oldest Indo-Aryan (i.e. Sanskrit) and Indo-Iranian (i.e. in a language called
Ephedra twigs were common and important in both cemeteries. Were they related to the “Soma” in ancient India (Vedas) and/or “Haoma” in ancient Iran (Avesta)? Were the Ephedra twigs related to the body painting (whitish sticky materials painting on skins of the dead)? Was there a common use of Ephedra plant in more nomadic groups in the Eurasian Steppe?Yang, Yunyun, Shifting Memories: Burial Practices and Cultural Interaction in Bronze Age China: A study of the Xiaohe-Gumugou cemeteries in the Tarim Basin, URN: urn:nbn:se:uu:diva-386612 via Eurogenes.