This humble agua can be a closely protected secret recipe amongst many latin/amer cooks. I had one yesterday at Armenia Restaurant on Alvarado/Montrose that could only be described as succulent (the pupusas were pretty good, too).
Not too sweet, scarcely a hint of the over-used Mexican vanilla flavor and rich with undertone of lightly toasted rice. The lady who made it was clearly very proud of her recipe. Since I don't drink, the wine piece of the chowish experience is denied me and I am now actively soliticing shout-outs from fellow agua fresca lovers.