Agassi admits now that that was a lie. He reportedly writes in his book that "Slim" was the person who introduced him to crystal methamphetamine by dumping a small pile of powder on a coffee table. ("I snort some. I ease back on the couch and consider the Rubicon I've just crossed.")
Embedded below is a 45 second television commercial for Mountain Dew starring Andre Agassi which is from that same era. Given his lying explanation to the ATP, it's perhaps unintentionally ironic today.