"trailer park candy" refers to any form of methamphetamine, which is stereo-typically viewed to be most commonly used by those living in trailer parks.
Jim:"Hey, heard about the big bust."
Dave:"Yep, confiscated about 20 kilos of trailer park candy."
A term used to describe any form of meth, meth being the stereotypical drug used by stereotypical people living in a trailer park.
Son: "Mommy, where's daddy?"
Mom: "He's in jail honey."
Son: "Why Mommy?"
Mom: "You father had a trailer park candy problem."