However, here are some options that are close or could be used in a playful context:
Similar meaning:
* Snooze: This is a very common synonym for nap.
* Catnap: This is a short nap.
Rhyming but not exactly the same meaning:
* Crap: This is a slang term for something bad or worthless, but it rhymes with nap.
* Snap: This could be used metaphorically to describe a short, sudden nap.
Ultimately, the best "slang rhyme" for nap will depend on the specific context and what you want to convey.