Boiling Water

• Mix 1/2 cup salt in 1 qt. of boiling water and pour the brine directly down a drain. The salt acts as a mild cleanser and works to dissolve any slime or scum along the sides of the drain. Boiling water removes grease or other scum along the drain as well. Together they can remove and eliminate the cause of the odors. Boiling water can crack some types of pipes. If you want to err on the side of caution, just use hot tap water.
  
  

Vinegar

• Pour 1 qt. of white vinegar directly down your drain. The white vinegar not only dissolves anything sticking to the sides of the drain, but overpowers the odor with the smell of vinegar. Vinegar is an odor eliminator. The "pickle" smell quickly dissipates, leaving a cleaner smell behind.
  
  

Baking Soda

• Baking soda alone, or combined with white vinegar, makes an effective drain cleaner. Pour 1 cup of baking soda into a drain. Follow it with 1 qt. of white vinegar and let it foam up and work into the drain. Leave it for about 30 minutes. Run the hot water for several minutes and rinse it out.
  
  

Bleach

• If you're sure the drain itself is completely clear, you can pour 1 cup of household chlorine bleach followed by 1 qt. of hot water down your drain. This effectively eliminates any bacteria left in your drain causing an odor. But do this with a clear drain only, as bleach can interact with several substances and chemicals, causing a toxic gas and reaction. Never pour bleach down a drain that has recently been opened with a chemical drain cleaner.