Stinky drains in the kitchen sink are normally the result of food particles hung up in the garbage disposal. The food particles start to decay, and you get an unpleasant odor coming from your drain. Use a brush on the teeth in the garbage disposal to remove food particles. Add a cup of bleach to the drain before bed, and allow it sit in the drain overnight. You may also try a baking soda, and water solution added to the drain. Yes the garbage disposal should be in the off position when cleaning it with a brush.
If the stinky drain is in the bathroom it’s probably a result of hair trapped in the drain. Over time it starts to rot, and can be very odiferous. Remove the drain plug, and pull out any material attached to the rod. You may need some needle nose pliers to reach some of the material. Pour a cup of bleach down the drain, and your odor problems should disappear.
If the odor is coming from a floor drain it could be sewer gas coming up your drain. The best way to eliminate this is with an enzyme based drain treatment. Pour a half of a cup of the enzyme down the drain once a week. It should solve your odor problem.