I take your point about P.C., though. Maybe “beverage” is the answer. It's neutral, and doesn't encourage the jury to make character judgments.
If the prosecutor uses the term "iced tea" in his opening statement, I think the defense should regard it as a demonstration that the prosecutor isn't interested in the truth. Don't get into the reasons of why the prosecutor might have wanted to avoid mentioning watermelon drink--merely observe that a prosecutor who can't be trusted to get little facts right shouldn't be trusted with big ones.
On a more general note, I wonder how many opening statements the defense is going to have prepared? What the defense says should depend upon what the prosecutor says. If the defense opening statement includes information which could only be supported by having Zimmerman testify, then unless Zimmerman testifies and subjects himself to cross-examination the prosecutor would be entitled to call attention to Zimmerman's failure to testify to back up his counsel's claims. On the other hand, if the prosecutor includes statements regarding Martin's supposed whereabouts, defense counsel could use those statements as justification for why Martin could easily have gone home had that been his intention.
Fundamentally, I think the primary focus of the defense should be that Trayvon Martin is dead because he decided to viciously attack George Zimmerman in an apparent effort to kill him [GZ's injuries would constitute prima facie evidence of TM's intent]. If the prosecutor uses the highly prejudicial term "victim" to describe TM, the defense should note that GZ the victim of TM's unprovoked attack. It may also be good to note that GZ volunteered to assist the police as a neighborhood watch captain not because the police or anyone else told him they needed to do so, but because he wanted to be a good citizen [key point being to set up the distinction between ordering someone not to do something, versus saying that it is not required, so as to refute the prosecutor's claim that GZ was ordered to stay in the truck].