A stubborn stain, odor or even a clog can quickly turn any sink into a nuisance. Clean drains regularly to prevent odors. If you find water no longer drains properly, you can use a quick do-it-yourself fix to have your sink working properly in no time.
Use a plunger. Fill the sink with enough water to cover the drain and bottom. Press the plunger firmly down over the drain to create a tight seal and give it several quick plunges. Plungers work great on bulky, not too strong clogs in toilets. Pull out the plunger's inner skirt to fit the drain, plunge, and rinse in clean water as the bowl refills. Keep a separate plunger for the toilet. Some plungers include a tidy storage caddy.
Use a barbed plastic drain cleaning tool. This is an inexpensive long, stiff but flexible plastic strip with a series of plastic barbs swept back from the tip. Stick it in the drain and pull it out. The barbs are somewhat strong and sharp: do not draw them past your hand. The tool can be cleaned with toilet paper or a paper towel dragged "with" the barbs, stored and reused. It works great on a strong clog near the drain opening, such as bathroom sink or tub soap and hair.
Blast a stubborn clog out of a drain using a wet/dry shop vacuum. Most shop vacs have an output blower mode that should be powerful enough to clean the drain clog. Hold the end of the vacuum tube firmly over the drain and create a seal around the tube using a towel. Make sure any other drain openings are closed or tightly plugged. Turn the shop vac to blower mode. Quickly turn the power on and off repeatedly until you dislodge the clog from the drain. Leaving the blower to run continuously for a long period of time can damage your pipes (or the vacuum, if its air flow is restricted). There are faucet-water-pressure drain cleaning tools that work on similar principles, which should deliver much more force than a shop vac: force for which drains may not be designed.
Wrap a heating pad around the trap pipe under the sink if you know your drain is clogged with grease from cooking. Turn the heating pad on to warm up the pipe, then run hot water through the drain until the grease clears.
Buy an inexpensive cable auger, or plumber's snake. You may also be able to rent one from a hardware store. While the cables coiled on a spool come in many lengths, a 25-foot (7.5 m) cable should be plenty for most household needs. Remove the sink trap under the sink using a pipe wrench. Have a bucket close by to catch any water that drains from the pipe after you remove it. Slowly push the auger cable or snake into the pipe opening until you feel resistance. Crank the handle on the auger while pushing the coil firmly into the pipe. The auger will slowly drive deeper into the pipe and through the obstruction. Continue the process until the clog is cleared and you are able to push the coil through the pipe with no resistance.
Treat buildup biologically. Use an enzymatic or bacterial drain cleaner overnight periodically for working but slow drains due to buildup. Follow the directions on the package. These are subtle and, hopefully, effective over time. They are not all exactly the same, so experiment if one does not show progress.