General maintenance of drains is good for eliminating odors and breaking down build up before it becomes problematic.
To freshen drains pour 1/2 cup Baking Soda down the drain then follow with at least 2 cups of boiling hot water.
If you have a slow moving drain pour 1/2 cup Baking Soda followed by 1/2 cup White Vinegar down the drain. Cover drain with a plunger if you can. Let fizz for up to 5 minutes then flush with one gallon of boiling hot water. Plunge if needed.