The fizzing combo of vinegar and baking soda is a great way to unclog and remove odor from a tub drain. Pour half a cup of baking soda in the drain, then follow with a mixture of one cup white vinegar and one cup of hot water. Immediately plug the drain with a rag to keep the bubbles contained for 10 minutes. Rinse by pouring a kettle of boiling hot water down the drain.