Only when the sprayer is used? Might it be that you're spraying hot water into the drain and this is causing more smell to be released than when hot water just runs into the drain without the sprayer?
A good fix for a stinky kitchen drain we've found is to put about 1/2 cup of baking soda in one drain, put the stopper in the other side, then pour two quarts of rapidly boiling water down the drain. The water must be boiling. Baking soda reacts to boiling water similarly to how it reacts with vinegar, but vinegar and baking soda neutralize each other too quickly to do much cleaning work. Repeat for the other side of the sink.
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