How do I unblock drains and remove smelly odor from drains?

Which drains? All or some?

Most bathroom sink clogs are caused by hair so hair conditioner works most of the time. Pour about a quarter cup with equal part water into drain and let it sit about 30 minutes. flush with hot water and baking soda for the smell, Repeat if necessary.

Works for me.

White vinegar helps with odors!

Need help with my kitchen sink.

Clear the drain of any hair. Pour some baking soda down the drain. Then pour some vinegar down. Let foam up. Then go with hot water down the drain.

If it's the kitchen disposal, use a rough sponge to o clean or dislodged any food particals stuck on the drain. Throw out the sponge. Then for nicer smells you can buy stuff but it works for only a short period of time. Use orange peels or apple peels or any other sweet smelling fruits. Important thing is no matter what you do. It should be cleaned out weekly. So dollar store package of sponges are great