Yogurt should be covered with a lid in the fridge to prevent it from absorbing odors and flavors from other foods, and to maintain its moisture content.
When storing yogurt in the refrigerator, it's crucial to protect it from the surrounding environment. A lid provides a barrier against airborne contaminants and prevents the yogurt from drying out. Cloth, while seemingly breathable, doesn't offer the same level of protection. It can allow odors and flavors to permeate the yogurt, altering its taste and quality. Furthermore, cloth can become damp and potentially introduce unwanted bacteria. A tight-fitting lid, on the other hand, creates a more controlled environment, preserving the yogurt's freshness, texture, and flavor for a longer period. Using the original container lid or transferring the yogurt to an airtight container is the best practice.
If you don't have a lid, use plastic wrap pressed directly onto the surface of the yogurt before covering the container with foil. This minimizes air exposure and prevents a skin from forming on top.