The first thing you want to do is to figure out what’s wrong. If your sink is leaking from the drain, then you’ve got a drain pipe leak. If your sink is leaking from the faucet or some other place, then you’ve got a different problem.
The most common cause of a sink drain leak is the connection between the drain and the pipe coming out of the wall. The connection between the two always has a rubber washer and sometimes a metal washer that can become corroded or damaged. The washer is what creates a water tight seal between the pipe and drain.