Remove the tips of the green beans and slice onions into thin strips.
Drizzle with about a teaspoon of olive oil and 1/2 teaspoon of balsamic vinegar. Season with a little salt and pepper. Don't overdo the salt as there is the teriyaki sauce later - just a pinch would do.
Roast green beans and onions in oven for about 20 minutes at 200C/400F.
While green beans and onions are in the oven, combine 1/2 teaspoon brown rice syrup (or other liquid sweetener like agave) and 1/2 teaspoon soy sauce.
When the green beans and onions are ready, remove from oven and plate it.
Drizzle the teriyaki sauce evenly over the green beans and serve.