If it's a drugs test we're talking about here, then it's one of those questions where you might get a different answer for every person you ask. In my opinion, baking soda does not, and can not, help you pass a test.
The myth seems to come from the fact that baking soda (or, to give it its scientific name, sodium bicarbonate) is often used as a cleaning agent, such as in toothpaste, or for ridding the body of excess acid, for example if you suffered from heartburn.
Excessive Consumption of Baking Soda is Dangerous
If you must try it for yourself, do not do anything foolish as to consume an entire jar or box of baking soda, as this is likely to do you serious harm or even kill you.
It may sound dull, but the best way to pass a drugs test is to keep clear of drugs. To check out other people's opinions on this subject here at Blurtit, check out How Do You Pass A Urine Test Using Baking Soda? or How do you use baking soda to pass a drug test for meth? or maybe How many hours before drug test should I do baking soda?
In this YouTube film, a professional chef gives his advice on drinking baking soda.
It might be worth check out if you're thinking of doing this yourself!