“Sparkling, still, or D.C.’s finest?” It’s the no longer particularly funny question that serves as a standard start to many a dinner out. I always go for the latter; I’m not paying for San Pellegrino in this or any economy. But next week, even the tap water is going to cost you. That’s if you care to make a small donation for it. From March 22 – 28, over 100 local restaurants have signed…