People who play sports launder most of their athletic gear regularly to eliminate any chance of foul odor. But one item, the humble sports watch, may escape notice until the dried perspiration on the watch band breeds bacteria which, in turn, cause foul odor. If your watch is waterproof, you can simply hand-wash it as you'd wash a delicate item of clothing. If your sports watch is not waterproof, you'll have to get a little more creative to clean it.
Set the watch out in a well-ventilated area until any perspiration or other moisture on the watch band it is completely dry. Remove the watch body from the watch band and set the watch body aside if possible; if not, continue with the entire watch.
Lay the watch out on a sheet of old newspaper. Sprinkle baking soda liberally on both the inside and outside of the watch band. Don't discard the extra baking soda that filters down onto the newspaper.
Fold one side of the newspaper over the watch, fold the ends in toward the watch, then roll the newspaper up like a burrito with the watch and extra baking soda inside.
Shake the newspaper gently for a few seconds to distribute the baking soda on the watch band.
Leave the watch in the newspaper overnight. Open the package and shake any baking soda off the watch. If the baking soda has adhered to the watch band surface, you can blow it off with a can of compressed air or a hair dryer, or very carefully vacuum it off with the narrowest hose attachment on your vacuum.