The plural of soda is sodas. The word comes from the Arabic, meaning Saltwort.
Historically, soda was obtained from the ash of the Salsola soda, more commonly known in English as Opposite Leaved Saltwort, or Barilla Plant, and other saltwort plants. Soda ash is one of the alkaline substances that are crucial in glass- and soapmaking.
Soda can also refer to soft fizzy drinks (especially U.S. English).