One of the most obvious advantages of polystyrene foam is that it has superior insulating properties to alternative products.
Foam foodservice packaging excels at keeping hot foods hot and cold foods cold. In fact, a hot drink in a plastic-lined, paper cup loses twice as much heat as the same drink in a foam cup over the course of just 10 minutes. In addition to their superior insulation properties, foam cups also hold carbonation better than paper alternatives. In fact, a soft drink in a foam cup will have more carbonation in it after 15 minutes than the same drink in a paper cup after two minutes.
Most paper cups require a plastic coating to retain liquids. Unfortunately, when a paper cup is coated in plastic, it is no longer biodegradable or easily recyclable. Foam cups also protect hands from hot beverages like coffee or tea, while paper cup users often add a cardboard sleeve, wrap layers of napkins around the cup, or even stack two cups together to achieve a barrier to the heat.
“Double cupping”  paper products creates over twice as much solid waste by volume, over five times as much solid waste by weight and nearly twice as many greenhouse gas emissions as using a single, average-weight foam cup. Furthermore, commonly used foam foodservice products like cups, plates and sandwich containers use significantly less energy and water during manufacture than comparable paper or corn-based alternatives.