You shouldn't drink the water in Vietnam under any circumstances. Tourists to Vietnam should also avoid brushing their teeth with tap water at all costs. The water in Vietnam is not safe to drink, and contains organisms that could leave you exposed to cholera, diarrhea, dysentery, giardia, gastroenteritis, hepatitis A, and typhoid fever. Ice in Vietnam is generally okay to drink. Most restaurants and street food vendors use machine-made ice that uses filtered water.