Tokens are made of metal, as are coins. Coin collectors are taught to never clean coins. Why? When a metal object is cleaned, usually the cleaning can be detected, at least by an expert. Coins that are known to have been cleaned, have an unnatural appearance and a reduced value. So cleaning a coin, or a token, will ruin its appearance and lower its value.

There are two exceptions that I know of:

1) Cleaning to remove surface dirt. If there is some crud on the token, you can remove it with water and gentle rubbing. Never use an implement of any kind, even a soft toothbrush. Any implement will leave marks on the surface of the token.

2) If the token is already well worn, meaning that the surface is already full of scratches, you can do little to further damage it.