This link "Quick note: Eating is the key to long distance biking" says,
If you don't eat, you have an hour, maybe two, of energy stored up.
Fortunately it's prescriptive too, saying,
And what should these calories be?
Well, something easy on your stomach
and fairly light. There are special
sporting-related products that are
generally right around 100 calories
and super-easy on your stomach, but
you don't have to go overboard. A
piece of fruit or some candy or even a
can of soda will work just fine. Just
try to keep it around 100-200 calories
maximum per hour.
... so that answers that: only about 100-200 calories an hour. Apparently you don't try to to keep up with the approx 500 calorie/hour rate at which you're expending calories.
As for what, this recommends bike-specific stuff based on maltodextrin, brand name "Hammer", and says that the body can't absorb more than 200-300 calories an hour - but that's for a multi-day ride.
Whereas this recommends:
- Junk food (donuts, gummi bears, etc.)
- Nuts (or peanuts)
- Olives (salty, light-weight, and high-calorie: though I'll guess slow to absorb)
- A Subway sandwich but without any hot/spicy components
- Ice tea (sugar and caffeine)
- Fruit (bananas, banana chips, fig bars)
- Cereal bars
To answer the "how much to drink?" question:
- This says, that 'one litre per hour' is on the high side, that that's for endurance not recreational rides.
- This says 16 oz / 45 minutes (~ 0.63 l/h).
- This says 28 oz / hour (~ 0.83 l/h).
- This says a couple of big swallows every 15 minutes.
One of those articles also says that you thirst after dehydrating 1% and suffer when you drop 5%. I weigh 77 kg so I suppose I'm 46 litres of water, so 1% is about half a litre. If I don't drink when riding then (if I ought to be replenishing up to a litre an hour) that predicts that I'd be thirsty (1%) within 1/2 hour or an hour, and suffering (5%) within 2 1/2 to 4 hours.
This says that "Sports drinks have low-sodium levels in order to be appetizing to the general public" and suggests 500 to 700 mg of sodium per litre. Salt is 40% sodium, so that's 1.2 to 1.8 grams of salt per litre.
1.2 g salt is about 1/2 cc or 1/5 tsp (per litre of water), which is less than I'd imagined.