Since the egg cream question comes up on the board here from time to time, just a note to say I discovered this evening that Parkway Deli in Silver Spring (Grubb Road close to Red Dog Cafe) does them ($1.90) and they use U-bet syrup. They also have the syrup for sale in the little store up front. I only learned this on the way out so I didn't have a chance to try one, so I can't vouch for whether they are up to the standards of, say, Gem Spa on 2nd Ave (or is it 3rd Ave.?).
Anyway just thought someone might like to know.