If you explore Lily's Mexican Market, definitely spring $1.59 for the horchata soft drink that you can buy at the takeout counter in back.
The horchata is the lighter-colored soft drink running through one of the two "jetspray" machines across from the counter. You pay for a cup, and you fill it yourself. The horchata is a refreshing, mild drink. It tastes smooth and lightly sweet, creamy but still refreshing. The other drink is tamarind, a flavor that I have previously recommended in candy and other drinks although I haven't tried that specific drink yet.
Wikipedia has an entire article that describes different drinks described by the same word. I think Lily's version is the rice-based drink that is one of the three typical flavors of Mexcian aguas frescas.
If you haven't been to Lily's, you should definitely try Howard County's best Latin American market. Click here for all the posts about Lily's -- including ones about chips, takeout tacos, fresh corn tortillas, tamales, and more.