Sugar – Vietnamese burnt sugar beverage

A while ago we ate at a Vietnamese restaurant in San Francisco's Chinatown. We were given these nice burnt sugar-flavored beverages to drink, but unfortunately the staff did not speak fluent English so I don't know what it was called.

I've tried in vain to research it but can't find anything close.

The beverage was very dark brown, but served with milk (I'm quite sure it was dairy milk, not coconut milk) poured on top, which when mixed turned it a caramel color. The consistency was thin, but the beverage was very flavorful—the burnt sugar flavor would have been almost bitter if it didn't have the milk added. Burnt sugar seemed to be the only major flavor—it was not a coffee beverage, though there might have been other spices. The beverage was sweet, but not extremely sweet. It was served in a standard plastic restaurant glass with ice.