Commonly used Australian slang, although possibly not of Australian origin. The phrase sounds modern but has been in use since the 19th century, albeit originally referring to honey rather than beer. Marion Harland included this in her 1857 work Moss-side:
"Piled-up [honey]comb,... which dripped with amber nectar."
Toward the end of the century the term became associated with beer, as here in the Californian newspaper The Fresno Weekly Republican, November 1893:
"At last, after a prolonged course of courtship, beer and sandwiches, the ardor of the fickle swain cooled. He no longer partook ecstatically of the amber nectar..."
Soon afterwards, in 1898, The New York Times had this:
"I want no tricky wine, But amber nectar cling to me... Haste the beer to me!"
There may have been earlier uses of the phrase in Australia, but I can't find them. It remains associated with that country though and was adopted as an advertising slogan for the Australian brewery Foster's.
Foster's and other Australian breweries exploit the hard-drinking parched stockman image in their marketing. Foster's also used Paul Hogan in one campaign, with the line 'like an angel crying on your tongue'. Stereotype or not, the unique Oz approach to life has led to enough names for beer and its containers and effects to deserve a dictionary of their own. Just a few of the many others are: