Combine four parts water and one part vinegar. Either apple cider vinegar or distilled white vinegar works equally well in the solution. Place the stained nickel plated item in a bucket or bowl and pour the solution over the top, until it completely covers the stain. The acidity in the vinegar helps lift off stains and restore the natural shine of the piece. The next day, wipe off any liquid from the piece and gently buff with a soft cloth.
Several solutions using ammonia clean nickel plating. Try using equal parts water and ammonia, mixing the ingredients in a bucket or bowl. Drop the item inside the solution, while wearing rubber gloves that protect your hands. After 30 minutes, remove the object and polish with an old toothbrush. If the diluted ammonia does not work, then use pure ammonia. Drop the nickel plated item in the ammonia and remove after five minutes or less. Wipe off any excess ammonia and buff with a soft cloth or old toothbrush. When using ammonia, always work in a well-ventilated area. Use caution, as ammonia can strip the nickel platting from the object.
Metal polish may work on some minor surface stains, including red wine. Pick a non-abrasive polish specifically designed for metal or chrome. Rub the polish onto the stained area and let sit for a few minutes. The stain begins absorbing the polish, which breaks up the molecules of the red wine. Gently buff the nickel plating with a soft cloth, rubbing off the polish and taking the stain away at the same time.
For larger or deeper stains, clean the item with a little liquid dish soap and warm water. Dry the piece with a soft cloth. Rub an aluminum oxide sanding block over the stained area. The sanding block removes deeper stains without damaging the metal. Fine steel wool with a 000 grade works the same way as the sanding block. Use a small amount of metal cleaner, which provides the friction for the sanding block and helps further reduce the chances of scratching.