You're there as a first date. No need to explain anything that you order. I take a seltzer water with cranberry juice and lime. Looks like a wine spritzer, to be honest. One work function left everyone wondering how on earth did I get the tall glass? Some places stick a straw, it's no biggie. I didn't have to explain much of anything. It was a preference. It was a luncheon, I needed to pick up the kids.
But as a dating point, if you aren't a drinker and they are, sort of a flag moment, to be honest.