Welcome to Vietnam!
What better way to immerse oneself in a foreign culture than by experimenting with the local street food?
Take a stroll down a friendly-looking and delicious-smelling side street that's off the tourist track, and have a taste of what the true Vietnamese people are happy to line up for.
I won't ask what's the worst that could happen, because it might scare you off. But keep in mind that there's only so much liquid you can handle before you need to make a mad dash for a toilet, a limit to the chillies you can take in any given dish without a cooling beverage handy, and there's nothing quite like the triumph of ordering your favourite coffee without having to point and gesture wildly to describe your request.
Good luck, and happy travels. :)
v1.0 - Super basic drink and food choices, no potential for harm. Eat all the things with no regrets!