Insomniac rhymes with:
eniac, maniac, megalomaniac, nymphomaniac, amnesiac, cardiac, eniac, kodiak, maniac, megalomaniac, nymphomaniac, pontiac, zodiac
Insomniac sounds like:
imagines, imaging, imagining, immunizing, inasmuch, incense, inching, incisions, incomes, incoming, ingenious, ingenuous, innocence, inocencio, insouciance, ionizing