When inside a Mr. Tasty ice cream truck, one of the the songs the truck plays is called the GTA Theme, in a cycle order it is usually played after Flight of the Bumblebee.
While playing the song, call ZiT, and a text message will confirm telling you the name of the song.
As soon as the message is answered, a Cheat Activated confirmation will appear, and the cheat will appear in the Cheat section in your phone.

Effects: Cheat gives you full health and body armor.