Common causes of squeaky bike break usually tend to be brake pads that are in need of a good cleaning, dirty bike rim brake surface or brake pads that strike the rim evenly across the surface or with the rear part of the brake first. Brakes that are “toed in” are most effective. This means the front end of the brake pad is positioned at a slight angle, so the front portion of the brake pad touches the rim first when you apply the brakes.
Loosen the brake.
Remove pads from the brakes.
Clean the surface of the brake pad with cleaning cloth.
Reattach and tighten the brake pad back to the bike.
Check to see if the brake cable is connected to the brake.
Test the brake.