My friend told me about these cups at Jamba Juice that he saw that did not condense water on the outside when there was a very cold beverage inside.
Does anyone know how it works?
The cups have an inner and an outer surface separated by an air gap.
Or a vacuum gap, a la a thermos bottle.
Condensation forms on any cool surface. The water vapor in the (warmer) air turns back into a liquid just because it’s now below the dew point for the atmospheric condition.
So the basic answer is that any sort of “anti-condensation” cup is highly insulated, so that the coolness of the beverage isn’t transmitted to the surface of the cup. The insualtor could be air, or a vacuum, or some other insulating material.