Some Imperfective verbs in -ся have a passive meaning, like продавђться 'be sold' (cf. продавђть 'sell'):
  Гдљ продаётся газирћванная водђ? Where is soda pop sold?  
Do not try to make up passive forms of this kind, because they often have a bookish or bureaucratic flavor, though продавђться isn't too bad. In conversational style use the third plural passive:
  Гдљ продаєт газирћванную вћду? Where do they sell soda pop?