It is usual for the vials to look empty because the powder inside is lyophilized, so the contents will stabilize and have a longer shelf life.
The lyophilization process freeze-dries the glutathione powder and nutrient booster liquid solution first. A vacuum then evaporates the ice. The resulting powder shrinks and compacts at the bottom because there is no air and moisture.
For a basic idea of lyophilization, please see this link.