The primary ingredient in traditional Mexican horchata is rice.
Mexican horchata, often called horchata de arroz, is a sweet, milky-looking drink made by soaking and blending white rice with water. Cinnamon is a characteristic flavouring, and recipes may also include sugar, vanilla or other spices. It is commonly served cold as an agua fresca alongside tacos and other Mexican foods.
Horchata has a much broader history than the Mexican version. Spain’s horchata de chufa is made from tiger nuts, while earlier grain-based drinks were associated with barley. The idea and name travelled from Spain to the Americas, where rice became the defining base of the Mexican style.
That regional variation explains a common quiz trap: “horchata” does not mean the same recipe everywhere. In Valencia, tiger nuts are traditional; in Mexico, rice is the standard foundation. Other Latin American drinks using the name may include seeds, grains or herbs, but rice remains the canonical answer for traditional Mexican horchata.