Other forms: adulterants
An adulterant is a substance that's added to a food, medicine, or other substance that makes it less effective or unsafe. High fructose corn syrup is sometimes used as an adulterant to make honey cheaper.
Adulterants are almost always added as a money-saving measure; they consist of substances that are less expensive than the actual product. Adding chicory to coffee without noting the addition on the label makes the chicory an adulterant. Water can be an adulterant too, if it's used to dilute a medication in order to make it cost less (and be less effective). The Latin root of adulterant means "to falsify or alter."