Under an hour, you need nothing. Over ninety minutes, you need carbohydrate and water.
Sports nutrition is an industry, and industries complicate things. For the runs most of us do, it is simpler than it looks.
Genuinely worth saying: this is general information, not advice for you specifically. If you have a medical condition, diabetes especially, talk to someone qualified before changing how you eat around exercise.
Before
Under an hour: nothing required. Run fasted if that suits you, eat if it doesn’t. It makes very little difference at this length.
Over an hour: something with carbohydrate one to three hours before. Toast and honey, a banana, oats, rice. Low in fat and fibre — both slow digestion and both make themselves known at kilometre eight.
The Tuesday problem. For a 22:00 run, your last proper meal was probably lunch. Something small around eight o’clock — a banana, a slice of bread with jam — makes the last few kilometres considerably better.
During
Under 60–75 minutes: water if you want it. Nothing else.
Over 90 minutes: you need carbohydrate, because your stored glycogen runs low. Roughly 30–60 g per hour, starting before you need it rather than after. Gels, dried fruit, sweets, sports drink — whatever your stomach tolerates.
Practise it on training runs. Race day is the worst possible time to discover that a particular gel disagrees with you.
After
Within an hour or two, eat a normal meal with carbohydrate and protein in it. Around 20–25 g of protein is the usual figure for repair. You do not need a shake; eggs, yoghurt, beans, meat, lentils all do the job.
There is no magic thirty-minute window. It is more forgiving than the marketing suggests — but after a long run, sooner is better than later.
Water, and Yerevan in August
Drink to thirst most of the time; it is a better guide than a schedule. In real heat you also lose salt, so on long hot runs something with sodium in it beats plain water.
And this city is covered in pulpulaks. Use them. That is what they are for, and the dog agrees.