And I would say that it is probably a great idea for you to not overindulge in this stuff. It is cheap for a reason and I've been kicked in the ass by it on a number of occasions. It is called Bia Hoi and it is served in dive bars all over the country. Some places give it away for free to entice people to come into the bar in the first place. Crowds attract crowds!
5000 VND is less than 20 cents US and when you first drink it, you probably will notice right away that it is not a wonderful vintage. I don't know what is in there but it tastes a lot like any other cheap lager but I also know that I have gotten some mean hangovers from this swill.
I've been told that this beer comes in many forms and the industry isn't regulated at all so you kind of gotta take what you get. It could be a good batch, it could be a mystery batch. Hell, it might not even be beer and it tastes a bit different every time I have a glass.
I was speaking to a bar owner / manager one day when the bar was giving away bia hoi in the hopes that people would buy nitrous balloons (more on that later) and I was wondering how it is that they are possibly making money with 20 people in the bar drinking for free. He informed me that the "keg" that they had on the bar that was driven by gravity and not a CO2 pump of sorts, costs around $10 for a full one. He jokingly said that they only have to sell 4 balloons in order to make their money back. I looked around the bar and saw that two people were having balloons so I thought "oh great, they're halfway there!"
I think that if you are in Vietnam that having bia hoi is something you should experience but for me, it 's just too dangerous to be a go-to. You don't know what is in it and every batch is different. So you are kind of rolling the dice on a lot of things here such as "what is the alcohol percentage?".... nobody knows. I've had a really mean hangover a couple of times from Bia Hoi so these days I tend to stay away from it. However, if you can control your consumption and only have a few glasses it can be a fun and really cheap night out!