I'm with Jenny on this.
No, I don't swig it from the bottle. But I do tip the bottle onto my finger, and lick it off.
There are different fish sauces, varying by depth of flavor, color, saltiness, etc. Has to do with the proportions of the ingredients used, how long the fermentation took place, and, I'm sure, other factors.
It's sort of like the differences between various soy sauces.
Generally I'm a fan of Three Crabs brand, which is the classic Nuoc Mam of Viet Nam. Recently I bought some Thai fish sauce for a recipe, and they're very different. So much so that if I put some of each in a shot glass, you'd think they were different products just by looking at them.
BTW, fish sauce, like anchovies, is used more as a salt element than a fishy one. It's one of those ingredients that you can't quite identify in a dish, but notice if it's missing.
Most people spoil garden things by over-boiling them... if they are overboiled they have neither any sweetness or beauty. Hannah Glasse 1745