The best thing to use is a product called GLUG, you can find it at your plumbing supply store. Somewhat hard to find at say home depot -- try to find a plumbing supply specifically. Glug reacts to any moisture at all, so be sure to use gloves and be extra careful not to get it on your skin -- no need to mention out of your eyes.
Only use glug or any drain clearing product if it ISN'T what i call a 100% stoppage, meaning some water is passing the clogged area. glug is no joke and once your pour the bottle inside your sink/drain, hold your breath, pour you hot hot water (ideal = boiling) in and clear the area, you don't wanna inhale it -- makes your throat itch like crazy.
let the room air out and it should of melted your clog away with acidity, allowing full drainage.
Pat Sementa Plumbing
677 van nest ave, bronx NYC
employee and slave for 28 years. just kidding i love it there.