One of the things you will appreciate more when traveling around Vietnam are the local fruits. They are always so fresh! You will find them in markets, shops and in the streets.
The list of Vietnamese fruits is almost endless: Custard-apple, Durian, Green-dragon, Guava, Litchi, Longan, Mango, Papaya, Rambutan, Sapodilla, Star-fruit, Water-apple, ... Should I go on? Some of them are available in our home countries, but nowhere do they taste as good as in Vietnam. Specially recommended is the Green dragon fruit.
Fruit juices should not be missed either. If you want to be safe, ask the clerk to remove the ice (most of the times it comes from tap water). But I have to tell you that I drunk thousands of juices while in Vietnam, and I did not have a single digestive problem.