Batman
According to this wikiquote page:
Batman: Good thinking, Robin.
-- "The Penguin's Nest", first aired December 7, 1966 (Wikipedia, season 2, number 61).
So Batman is 7th December, 1966.
Having searched through scripts + quotes of all the series, I couldn't see it, however this answer (Yahoo! answers) says:
"When batman gets a riddle from the riddler, he just says the riddle loud out and changes it into something completely random like from blueberry muffins to kitchen equiptment. (true story)
When batman solves the riddle Robin always goes "Good thinking batman!"."
That gave me the episode "A Riddle a Day Keeps the Riddler Away", from 16 Feb. 1966. However, I haven't checked if it actually does have it in by watching (no sound).
Maxwell Smart
"Good idea, 99" appeared in the episode "KAOS in Control".
-- atomicmpc.com
But that isn't quite it.
I can say that it appeared in the show "Perils in a Pet Shop" - season 2 episode 13.
(Script from springfieldspringfield.co.uk, then date from imdb.com).
That was aired, no kidding, 10 Dec. 1966 - 3 days later than it first appeared in Batman.
So Batman / Robin said it first as far as I can tell. It is not well known which episodes it was said by Maxwell Smart - I can make no guarantees that the episode stated above was the first occurrence.
Other, earlier uses
There was a series called "The Many Loves of Dobie Gillis:", and in Season 2, Episode 3 (Baby Talk) (18 Oct. 1960), Maynard G. Krebs says
Good thinking
but without any name (from IMBd.com list of quotes of Maynard G. Krebs).
I have not found an occurrence of "Good Thinking + Name"
Australia
The only australian refereces I found was in the bookcrosing.com forum:
Good thinking 99 - Greetings from NSW Australia
-- Glenasena - Jun 26 '06
(NSW meaning New South Wales)
REVISED
A lesson in the dangers of relying too heavily on Google Ngram (aka mea culpa)
Previously, I posted an Ngram chart illustrating my surprise that waffle used in its verb form seemed to not exist before the late 1950s. When using Ngrams I started with a much wider timescale: 1800 to 2008, I hadn't noticed the tiny bump that appeared sometime in the 1920s. My error, my fault and for that I apologize. Here is the same Ngram updated.
When I dug a little deeper, I found a quote dated 1913 using waffle in its gerund form. Here is a new Ngram chart with "waffling" included in the search. As you can see, it tells a very different story.
Notice how waffling dominates the map, making he waffled insignificant and irrelevant.
Furthermore, by sifting through the results on Google books I discovered that the term, waffling, refers to the art of making waffles and can be jokingly called a sport. On top of that, it's often used in the compound noun waffling-irons with and without the hyphen, and its past participle can be used as an adjective, as in a waffled breakfast, waffled toast, waffled potatoes, waffled surface, waffled chiffon, waffled material, waffled leather or a waffled quilt. (Who would have thought being an etymologist could be so exhausting!)
As a result, I still maintain that the question is not one of general reference. The scope for discussion is much wider than simply looking up waffle in Wikipedia.
A British speaker commented:
If someone keeps changing their mind, they are by definition being
vague and talking about nothing in particular. There could be other
reasons to (hiding something... not knowing what they are talking
about, etc) but that doesn't alter the fact that BrEng and AmEng agree
that indecisive people waffle.
I believe the difference is more marked than the one suggested by the user. And I'll do my best to explain why.
Collins Dictionary gives this definition
British English: waffle If someone talks or writes a lot without saying anything clear or important, you can call what they say or write waffle. He writes smug, sanctimonious waffle.
Word Origin C19: of unknown origin
Merriam-Webster offers
intransitive verb
1: equivocate, vacillate “waffled on the important issues”; also : yo-yo, flip-flop “she waffled when asked what she thought of her sister's new boyfriend”
Origin of WAFFLE
frequentative of obsolete woff to yelp, of imitative origin
First Known Use: 1868
1.
I'll include my personal definition of the BrEng sense of the word waffle which I left in a comment to the aforementioned British speaker who argues that there is no discernable difference.
Waffling in BrEng is primarily someone who keeps talking
endlessly about nothing in particular, it's like a drone sound, a lot
of words being said or written without coming to any conclusion. I wouldn't include hesitation or indecisiveness. The act of waffling could disguise someone's insecurity, as people do have a tendency to rattle on when they are nervous. Some, instead, become tongue-tied
From 1957 a British newspaper clipping (1957)
“... little darling that ever walked this earth! She's a princess! She's a
fairy! She's a — ” The rhapsodist broke off short, and flushed red.
“Forgive me,” he said “for waffling like that, but I don't quite know what I 'm doing just at present. Dad, I'm the happiest man that ever lived!”
2.
From The New York Times the AmEng sense
Wishy-washyness, often spelled wishi-washiness, is not synonymous with
flip-floppiness. I dealt with flip-flop, both noun and verb, a few
months ago, defining the side-switching not so much as a permanent
change of mind but with its verb synonym "waffle" (from the Scottish
waff, "gust of wind"; nothing to do with the Dutch wafel, "cake baked
on a grid").
The American journalist, William Safire, in this excerpt is
clearly saying that flip-flop is synonymous with waffle and not with verbosity or excessive wordiness. The journalist continues “The standard English synonym for the flip-flop verb is "vacillate."”
Another instance, which illustrates more clearly the difference between AmEng and BrEng use of waffling
Think of how much time you waste waffling between a yes and a no,
deciding whom to hire, where to locate your business and how to
organize your day. Now there is software that can make your choices
easier.
Source: InfoWorld - 15 Aug 1983 - Page 88
A British speaking person may have said “humming hawing” (US hem haw), “wavering” or “dithering” in its place. “Sitting on the fence” is another alternative.
- The earliest instance I found for "waffling between" is dated 1964 in the Ontario Library Review, Volumes 48-49
His hero is a 30 year old Catholic bachelor waffling between the
priesthood and love of a lass, who is, alas, both a protestant and a
librarian. This is a readable novel with many droll characters.
The earliest reference I found in Google books with waffled as it is used today is dated 1962 from The U.S. Government Printing Office.
It's interesting to note that the term waffled is described as local jargon and in the earlier clipping it is quoted, implying that the term was relatively new and considered almost dialectal.
Conclusions
The findings so far seem to suggest that the verb waffle as used in the UK and in the US is much more recent than any of the references or dictionaries I consulted have suggested. There is no evidence that proves that the AmEng verb existed (at least in print) before the 1950s. Whereas in the UK the earliest instance of waffled, meaning to speak at great length without meaning, is dated 1913.
Best Answer
As far as I know, it varies from region to region within the US. Personally, as a resident of the northeast US, here are the terms I would recognize:
I wouldn't recognize two cents plain or just sparkling. The former is an antiquated term according to Wikipedia. Also soda water is not something I hear very much and I'd probably figure it out after a few seconds of being confused.
I think most people are aware that the preferred term for plain carbonated water, as well as the meaning of several of these terms, varies from region to region, and so people are unlikely to find it strange if you use a term that is not the default in whatever region you're in. Technically there seems to be a difference between some of the various terms (e.g. source) but a lot of people are probably not familiar with those differences.
The variation in usage makes it difficult to find data on the relative frequency of using any of these words to mean one specific thing. For example Google Ngram may not be reliable because different people can mean different things when they say e.g. "sparkling water".