A can of baking soda
Baking soda, also called sodium bicarbonate (NaHCO3) is a dry, white powdery chemical compound that releases carbon dioxide when combined with certain acids.
In 2268, Leonard McCoy used a container of baking soda as a component of a gas grenade in an attempt to escape the Melkotian illusion. (TOS: "Spectre of the Gun")
Background
Baking soda was used by the visual effects department to create the sprays of snow as Voyager slammed into the planet in VOY: "Timeless".