never clean a collectable coin. take the coin to a dealer in the exact shape they are in and the dealer will guide you what to do. However, I highly doubt you have anything valuable so if you want to clean your little pennies that was minted in 2005. Go ahead and use baking soda.
Are these collectors coins?
You have to go by what they are made of...
Copper - a paste of salt, white vinegar, and flour
Silver - use aluminum foil, hot water, baking soda, and salt in a pan
Nickel - warm soapy water and a toothbrush
I heard vinegar cleans pennies