However, you could use near rhymes or eye rhymes depending on the context:
Near Rhymes:
* duh (a sound similar to "cuh" but with a slightly different vowel sound)
* huh (an interjection similar in sound)
Eye Rhymes:
* ugh (spelled similarly but pronounced differently)
* enough (spelled similarly but pronounced differently)
Ultimately, the best "rhyme" for "cuh" would depend on the specific context and the intended meaning.