The French brought coffee to Vietnam toward the end of the 19th century. Unlike tea in Tunisia, there were no epidemics. But the local coffee culture evolved beyond recognition. The drink here is usually cold, and instead of sugar, they add condensed milk. Lots of condensed milk. And they drink it. During the numerous wars that affected the country, additional varieties emerged. For example, coffee with egg. According to legend, there wasn't enough milk for the drink during the war, so in Hanoi they came up with the idea of whisking eggs and using them instead of milk. Taste-wise, it's actually not bad. But I didn't become a fan. There are also variations with salt, coconut, and even avocado.

Vietnamese coffee has many stories connected to it, but the funniest one happened with Germany. In the late 1970s, there wasn't quite enough coffee beans in the world for everyone who wanted them. In 1980, East Germany signed a deal with Vietnam where the Germans committed to supplying their communist brothers with equipment, technology, and all necessary resources for planting and cultivating thousands of hectares of coffee plantations. In return, the Vietnamese promised to give half of the entire harvest to East Germany. It all would have been fine, but when the harvest was ready, East Germany no longer existed, and there was no one to give the beans to ¯\_(ツ)_/¯

Anyway, if the local options don't appeal to you, there are plenty of decent classic cafés in the major cities. For example, here or here or here. Maybe you'll make it there someday.