Although Cinco de Mayo is not a national holiday celebrated in Mexico, in the US it has become a day of celebrating Mexican heritage and pride. Cinco de Mayo was commemorated in the late 1880s in the US - and naturally food and drink made their way to the center of the celebration. We've all had margaritas, cervezas, guacamole, salsas + tortilla chips, but there's also a popular border-town beverage called horchata that deserves to be part of the celebration.
Horchata is a traditional Mexican beverage that looks and tastes like milk, but it's rice-based. It is best served over ice. This sweet beverage has many variations (depending on Spain or Latin American influence) and can be flavored with almonds, cinnamon, sesame seeds, and vanilla. This beverage is good news for the lactose-intolerant, but better yet a perfect drink to finish-off spicy Mexican food; supposedly good for the stomach.
You can find horchata commonly served at Mexican restaurants or taquerias - on the menu under aguas frescas. Making horchata from scratch at home is also an option, but it is a very long process requiring a few days to make the rice-based milk. I suggest shopping in a Spanish market for good quality bottled versions or fine organic instant mixes.
For more Cinco de Mayo food ideas: