Here's why:

* Viscosity: Viscosity refers to a fluid's resistance to flow. Water has a low viscosity, meaning it flows easily. Soda also has a relatively low viscosity, though slightly higher than water due to the dissolved sugar and carbonation.

* Perception: The sensation of "thickness" in soda might be due to:

* Carbonation: The tiny bubbles of carbon dioxide in soda create a fizzy sensation that can make it feel thicker in your mouth.

* Sugar content: The sugar in soda adds to its sweetness and density, which can also contribute to a perception of thickness.

In summary: Soda is not physically thicker than water, but its carbonation and sugar content can create a sensory experience that makes it seem so.