Well, we know the amount of cups of sugar it calls per 1/2 teaspoon, so all we need to do to find the amount of cups of sugar per teaspoon is multiply by 2, since 1/2 teaspoon * 2 = 1 teaspoon.
2/3 * 2 = 1 1/3
The unit rate is 1 1/3 cups per teaspoon
Hope that helped =)