There is an interesting Q&A on independent.co.uk (though it dates from 1995) talking about bananas and tennis...
Q. Witnessing players at Wimbledon
chomping their way through pounds of
bananas between games prompts the question: who began this sporting food fad and are there sound nutritional reasons for the players' preference for bananas to other fruit or food.
In what other sports (leaving aside lunch and tea breaks in cricket) do the participants eat during the course of play? A.
The sporting fad for bananas was started by sports nutritionists such as myself.
The banana is rich in carbohydrate - an important source of energy for athletes and has significantly higher levels than any other fruit.
Also, unlike most other forms of high-carbohydrate foods, it contains very little fat but is also high in fibre.
The combination of fibre with the banana's three natural sugars - fructose, sucrose and glucose - means it provides a sustained boost to flagging energy levels, thus so many players at Wimbledon were seen eating bananas.
Bananas are also an excellent recovery food for replacing potassium lost in sweating , something most players must have been suffering from at this year's tournament.
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Jane Griffin, Consultant Nutritionist to the British Olympic Association, London SW17 Sounds like it would be good for long bike rides as well.
bicycles.stackexchange.com/users/417/dee-see
Real food like bananas are better than processed food any day.
Don't ditch old school foods.
Remember when they said that margarine was better for you than butter?
30 years later, they find out trans-fats are bad.
The banana stands the test of time.
Gel packs and bars won't.
Keep at it brother!
bicycles.stackexchange.com/users/790/Jeshizaemon
They are easier to carry than coconuts (although two of you could carry one on a line)
bicycles.stackexchange.com/users/427/mgb
I'm not a nutrition expert, but I swear by bananas!
I have always had issues with cramps and bonking on long rides (over 50 miles).
I don't train a ton because I have young children, but I like doing the Palm Springs Century each year.
The way to prepare for this for me is to ride my usual 20 mile loop around town first twice, then 3 times, and yesterday I did 4 laps for a total of 80 miles.
I had 4 bananas, one each hour, along with 2 large water bottles and felt great!
I have tried the GU Packs, sports drinks, sugary chomp bites, and none of them seemed to work.
From now on, it's just electrolyte water from Trader Joe's and good old fashioned bananas!
bicycles.stackexchange.com/users/5946/Dutch Cyclist
In addition to the points made in other answers, I think bananas are good because you can stuff one down in no time at all.
Like, less than ten seconds.
I think that's handy when you're on the bike.
bicycles.stackexchange.com/users/14375/BSO rider
I took a banana on a race a couple months ago.
It went from nicely firm and yellow to bruised, squishy and messy in a couple hours.
I binned it in the end.
Plus the ratio of packaging to content is pretty high, unless you eat the skin or carry it peeled.
Possible replacements - dried banana chips may work.
I tend to buy three things from supermarket bulk bins, a chocolate or carob bite, a yoghourt based bite, and something mostly nut or grain based.
Don't forget your water though!
bicycles.stackexchange.com/users/19705/Criggie
No one addressed the question of how long does it take for the banana to break down and work.
It can not be immediate.
I think two hours might be too long, but if the banana needs say 1.5 hours, you will need to eat something about one into your ride max before eating the banana for it to work 2.5 hours down the road.
To suggest gel and cliff bars don't work is also not right.
But you need the most important thing: water or Gatorade/water mix with the gels cliffs or the banana.
You need 80 grams of carbs per hour on a long ride, one banana wont cut it.
I like bananas but the fact that half the volume you throw away (the peel) makes this only a partial solution in my opinion.
bicycles.stackexchange.com/users/40711/richard brown
I am very much an old school cyclist and I always carry a banana with me when I go on rides longer than an hour.  In the past I have found them ideal - they easily fit in my jersey pockets, the wrapping is biodegradable (if I accidentally drop it when riding), high source of potassium to stop muscle cramp.    Should I change my ways and ditch the bended yellow pill for a more modern fare?
Are bananas still a good food to carry when cycling?
bicycles.stackexchange.com
<nutrition>
bicycles.stackexchange.com/questions/2145
bicycles.stackexchange.com/users/106/Anthony K
The combination of  fibre with the banana's three natural  sugars - fructose, sucrose and glucose  - means it provides a sustained boost to flagging energy levels,  thus so  many players at Wimbledon were seen  eating bananas.  Some people prefer bananas as they believe real food like bananas is better than processed food any day. Other, however, feel there is a lot of waste with a banan and thus think they are only a partial solution. Most people agree that the fibre and natural sugars found in bananas make them a good option, as they replenish waning energy and potassium levels. This is verified by personal experiences. The argument for natural food also adds to the point. However, you might want to consider that bananas are easily damaged, while half their volume consists of their peel.
Most people agree that the fibre and natural sugars found in bananas make them a good option, as they replenish waning energy and potassium levels. This is verified by personal experiences. The argument for natural food also adds to the point. You might want to consider that bananas are easily damaged, while half their volume consists of their peel.