Three basic chords on a guitar… may I suggest D, G and A?
As the tonic, sub-dominant and dominant chords (I, IV and V) in the key of D, you’ve just learned enough to play 90% of all folk and rock songs. They’re also some of the easiest chords to play.
If that doesn’t take all of your two hours, add a couple of minors, and an E chord (then you also have the key of A covered).
…
(Oh, same applies to a ukulele)
I once took a cooking class where they taught how to cut and slice vegetables and stuff with a real (large) knife. Took two hours, and I did learn how to cut stff in really tiny bits.
Use this skill almost every day. I could of course already shred stuff for cooking, but not in this way and not so good.
Can someone learn to solve a Rubik’s cube in 2 hours? (“useful” as far as bar bets and impressing your relatives go…)
Nit-pick… Single pin picking.
How long does it take to learn nit-picking? 
Anyway…
Basic cooking skills.
Eggs, boiled, scrambled, or fried
Spaghetti from a package with browned beef and sauce from a jar.
Bikes are a lot easier to ride than children.
Thinking back on my locksmith training, I recall being taught that lockpicking is “equal parts skill, art, and luck.” I was pretty good at it, but there always still plenty of locks that just wouldn’t ever pick for various reasons.
I think I could easily teach someone to drill out and replace a lock in two hours. Drilling is just drilling, and replacing the lockset is basically just a handful of screws. Repinning the cylinder is a bit more complicated, but I think I could teach a mechanically inclined person how to repin a cylinder in two hours. (I always really enjoyed repinning. It appealed to my meticulous nature.)
How to sharpen the blades on almost anything/everything: knives, chisels, planes, saw blades. Two hours would be plenty.
How to change your own oil/filter and air filter.
How to make a good pot of stock and then a good pot of stew.
And then you can add the blues to your repertoire. 
Basic First Aid A B C . US style?
A Are they insured?
B Are they breathing?
C Call a lawyer
Okay, then I’ll nominate sex.
Learning “how do you say” in other languages is an extremely useful skill, at least while visiting the country which speaks that language. With just that one phrase & hand gestures/signals you can go quite far in picking up the language.
I was a quick learner.
And I really enjoyed studying.
Pop quizzes were my favorite.
The problem is not pop quizzes. It isn’t even a multiple choice format, which I’ve always liked. It’s the long essay questions afterward.
Personally, I always enjoyed Independent Study.
Small study groups were also quite nice.
I can teach someone how to write simple SQL queries in two hours with no prior experience, which is shocking to many of the people at my company when they attend the class. Twice a year, I give a course of 11 classes to anyone in our company that is interested. On day 1 they haven’t done joins, aggregates, various string and date functions or any other more advanced topics, but data structures, data types, the SELECT statement and the WHERE clause are all covered in 2 hours.
It’s not worth much by itself, but I’ve had students take that knowledge and run with it and have seen their salaries skyrocket as a result.
Two hours is better than zero, but for someone wanting to learn a difficult foreign language then it’s essentially close to zero.
As I said upthread though, you could learn to read out various phonetically written languages.
It’s annoying seeing newsreaders butcher “Huawei” week after week and I’ve even seen whole video series on China where the presenter hasn’t bothered to learn how to read out pinyin. I didn’t persevere very long with such a series; if he can’t spend the couple hours, why should I?
It is important to carefully and completely remove the oil of the cat before burying it to avoid groundwater pollution, even if burying then takes over four hours.
You can’t learn a language in a couple hours. But you could learn perhaps ten basic phrases. That won’t help you communicate. People who do it think it makes them seem more worldly or polite, which it might, somewhat. That can go a long way.