"Fire Cider" according to most references that I can find was first coined in the 1970's by herbalist Rosemary Gladstar. It is essentially an oxymel (latin for "acid and honey") of warming herbs, with a formula that changes depending on the herbalist, the season, the plants available, etc. Some sources say that is is traditional to bury the mixture in the ground for a month before ingesting.
Fire cider is popular among dieters and body builders as a kick starter to metabolism, when used like this it is typically taken as a 1-2 oz "shot" first thing in the morning. Unless you are someone who LOVES Tabasco on everything, is a fan of a pickle back, and have done straight ACV (apple cider vinegar) before, I am going to suggest that if you want to try Fire Cider for this purpose that you start with 1 Tablespoon in 2 oz of water and go from there.
The other common use for fire cider is to burn away colds. Consumed straight or mixed in water, the warming herbs can certainly give you the rushing feelings of clear sinuses and may make your nose run. Recommended use in colds is 1-2 Tablespoons every 3-4 hours or as needed, as soon as symptoms appear. Or some people use 2 Tablespoons per day as a defense against cold season.
Like many common or traditional food based remedies there are not scientific studies on fire cider that I can find. But the benefits of components of the ingredients individually are fairly well known.
My Winter 2018/2019 fire cider contains organic apple cider vinegar (with the Mother), and features local buckwheat honey. A full list of ingredients is listed in the product description.