Unclog kitchen sink; have already tried vinegar, baking soda and salt.

https://www.thespruce.com/how-to-unclog-a-kitchen-sink-2718799

Try a drain snake.

Try boiling water first then add dawn dish soap just before pouring down or dollar tree has drain cleaner if your on a tight budge.

Turn off the water to the sink; the controls are in the cabinet under the sink. Turn both handles to the left until they are snug. Then, on the "U" shaped pipe, remove the nut on the bottom. Using your finger, and remove any blockage you may find. If you don't find anything there, put it back together and pour 'Liquid Plumber down the drain It can take a while to work, read the directions on the bottle. If it still doesn't drain, call a plumber. Explain to him (or her) what you've done so far.

Plumbers friend. You know that plunger with the suction cup on the end? They make them with short handles just for the kitchen sink. If you have a double sink make sure you cover the other side so that a vacuum can be formed.

Don't use the one you have for the toilet

Could something like a rag or such be in it???? Got a do-it-yourself plumber in the family or as a friend???

Remove the trap. Something may be clogged there. If not, with the trap open, you can snake the drain. If this doesn't work, call a plumber.

A snake works great, isn't toxic and can be used indefinitely...no opening pipes.