He's just trying to counter emotional manipulation with his own emotional manipulation.
He mentions the media spinning the contents of his drink can, that the media said it was iced tea first, and now says its watermelon (consequently, after the picture of it showed up). Then he made the assumption that Trayvon was using the watermelon drink to make "lean" with robitussin, yet no one found anything codeine based on him. I like Arizona Watermelon and skittles, and I've never made "lean" in my life.
What about the outcome of the case would be different if it were tea in the can instead of watermelon? What if he was going home to make lean? Does that make Zimmerman more or less innocent?
Assumptions like this are irrelevant to the facts of the case, and that's why this type of anecdotal evidence isn't permitted in court. We weren't trying to find a degree of guilt. It doesn't make Trayvon more or less guilty, it doesn't make Zimmerman more or less innocent.