I bought a 12-oz small for $2.39.
McDonald's describes the flavor of the Horchata Frappe as a mix of cinnamon, vanilla, and coffee. I didn't detect much in the way of vanilla but it did deliver the cinnamon rice milk flavor of horchata with just a hint of coffee at the tail end. It hits a good balance between the two as a stronger coffee flavor seems like it would be a weird duel of contrasting flavors. The drink was sweet but not terribly so.
The Frappe had a thick but drinkable texture. It was smooth with no chunks of ice.
Overall, McDonald's Horchata Frappe makes for a tasty rendition of horchata as a refreshing frosty ice-blended drink. Drinking horchata makes me want some tacos or nachos from a taquiera or food truck though.
Nutritional info not available.