The two main ways of getting rid of brake noise are
getting rid of free play in the brakes and adjusting them
so that the edge of the brake shoe closest to the front
of the bike contacts the rim first.

Grab a brake shoe and try to move it front to back, is
the brake tight, or is it sloppy? Getting rid of that
slop is the first step, but it may not be possible
with a two dollar brake on a sixty dollar bike.

Mitch.