I remember hearing about this lawsuit on the radio when I was a kid, and it being absolutely slammed as ridiculous overreach by the plaintiff. But since then, I've heard little bits about the case, and it seems like it may not have been quite so ridiculous after all...
The Hot Coffee case is really interesting from a sociological point of view.
As other posters have pointed out, the suit was in no way frivolous, a woman nearly died from McDonalds unsafe practices. Interestingly, there had been over 700 previous documented cases of others being burnt from McDonalds overly-hot coffee, McDonalds knew it had a problem.
What is interesting to sociologists is what happened after the case. McDonalds went into PR overdrive to control the discourse (what we 'know' about something) that it was a frivolous lawsuit. It used it's corporate strength to tell the story of the suit in a way that made it look like the victim. The public outcry that resulted led to legal reforms that were supposedly stopping such 'frivolous' lawsuits but were in fact protecting big companies from being sued over unsafe practices.
So the 'facts' that the public know about this case; that a greedy woman sued McDonalds because their coffee was hot- is exactly the story McDonalds created and wanted the public to believe.
Reading this answer sounds a bit like I'm anti-corporate, which I am not, as a sociologist this case is a great example of how powerful entities create discourse to suit their interests.
Good summary article here: https://www.vox.com/policy-and-politics/2016/12/16/13971482/mcdonalds-coffee-lawsuit-stella-liebeck
More on the power of discourse:https://www.thoughtco.com/discourse-definition-3026070
www.rd.com/culture/hot-coffee-lawsuit/amp/ this was in Readers Digest awhile back. She was severely burned over a significant part of her body, and the coffee was incredibly hot, so it wasn't frivolous. McDonald's required coffee to be served at 180 to 190F, which is really, really hot - consider that your water heater probably is set to 120 or less because of the risk of scalding.
It sounds frivolous, but the woman in question was hospitalized for quite a while, and the suit DID cause McDonald's and other companies to change their rather dangerous policy.
It would be similar to someone suing over food poisoning and changing company policy to require safe food-handling procedures.