Como se dice " agua de jamaica"
Flor de Jamaica is hibiscus in English, and the hot infusion thereof called hibiscus tea.
I've never seen it drunk cold in English and do not know of a standard name for it...
Bienvenido al foro!
This is the best I can make of it.
The water of the flower of Jamaica is very healthy.
El agua de la flor de Jamaica...
If we are discussing a hydrosol obtain from distilling the petals or other part of the flower it would probably be called Jamaican rose water. (like Rose Water or Orange Water). Otherwise, it would probably be called a juice, extract, syrup, tea, etc. of the flower depending on how it is derived.
"agua de jamaica" in Mexico is a known in the carribean as "sorrel". The leaves are dried, then boiled and you add sugar to the drink, usually around Christmas time.
I recall the first time I ever came across this drink. I was vacationing in Los Cabos, México and was wondering why would anyone call un refresco after a country, right? I was intrigued by this purplish liquid in a large jar and was quite pleased when I requested some from the puesto proprietor...bottoms up! (gringo's on point!)