Everything can be adjusted to taste. I went with a very light hand with the sugar and juice from only half a lime. (Maybe my limes were bigger than normal?) In his cookbook, David Chang says that this version is lighter and sweeter than whatever his Vietnamese chef's mother makes.
Combine the fish sauce, water, vinegar, lime juice, sugar, garlic and chilies in a jar.
This vinaigrette will keep for up to a week in the refrigerator. Supposedly. When you start taking little sips of it straight from the jar with a teaspoon every once in a while, it doesn't last that long.