From the introduction:
With this edition of Buy My Snake Oil you will find over a dozen different items that are dubious and practically worthless, despite their claims of powerful abilities and exotic sounding names. Though such snake oils are more or less useless to the adventuring party these items can be rather useful to the game master in a variety of ways. Use them to fill the otherwise empty shelves of the potion maker’s shop or have deceptive merchants hawk such wares on the open streets and in the village marketplace. The placement of crates of such items in a wizard’s fortress might encourage the characters to dump otherwise valuable treasure to add enough wagon space, only to realize that they had been duped once they arrive into town.