Alkaline batteries contain a base, which is what corrosion is made of. An acid like white vinegar or lemon juice will neutralize this base.

Lightly dip a cotton swab in white vinegar or lemon juice.

Don't soak the cotton swab. Only use a small amount of liquid at a time.

Gently rub the battery terminals with the cotton swab to dissolve and remove the corrosion.

The corrosion may fizz and bubble. Don't worry, this is normal.

Continue this process until there's no corrosion on the terminals.