Not Close to the proper spelling...Tine soonyet

But it sounded like Tine Soon-yet. Any ideas, my grandmother always used to say it and we say it too, but have no idea of its meaning.

Could it have been synek?

well, it would help a bit if you told us in what context/situations your granma was using it :)
but here's a rough guess: "tańcuje" which is (or rather was) a colloquial version of "tańczy" (which means "he/she dances/is dancing), the infitive form of the verb would be "tańcować" (instead of the correct "tańczyć" = "to dance")