Question: If "reek" is used as a term to describe something that smells bad, what word of equivalent meaning would describe something that tastes bad?

Answer: 
Just from the limited information given by the OP, he/she seems to be asking for a verb for taste with a negative connotation.

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> smell : reek :: taste : \_\_\_\_\_\_\_\_\_
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Taking the general meaning of "reek" as "smell bad," a comparable verb that, when used for taste, generally means "taste bad" is [**cloy**](https://en.oxforddictionaries.com/definition/cloy):

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> Disgust or sicken (someone) with an excess of sweetness, richness, or sentiment
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The meaning of "cloy" is not restricted to taste, but used in context it does have the basic meaning of "taste bad."

An example of it used in relation to taste:

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> Not everything works so well. Grilled octopus with potato is a bit dull. And a special of plump sweet diver scallops with vinegared rhubarb and white asparagus cream just misses the mark. The vanilla in the asparagus cream gives it a perceived sweetness that **cloys**.
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[*LA Times*, "The Review: La Vida" by S. Irene Virbila (May 13, 2010)](http://www.latimes.com/food/la-fo-review-20100513-story.html)
It's not a verb but maybe [pungent](http://www.merriam-webster.com/dictionary/pungent) [MW] would work for you

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> having a strong, sharp taste or smell
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