When riding for several hours, I try to eat about 200 to 250 calories every hour or hour and a half. Something like a half sandwich, energy bar or gel, granola bar, ice cream at a local store, potato chips, candy bar, etc. If riding all day (for me, six hours or longer is all day), I try to have some food every hour, not less frequent than that.
I specifically try to avoid having too much food at any one time, if I have a big lunch, that does not really help as much if I had kept riding and rationed out my calories better. I am 59 years old. I could handle bigger meals and more time between calorie intake when I was younger, but not now. The exception is that I might have as much as 800 calories at the very beginning of a ride.
I am a regular coffee drinker, one water bottle generally has iced coffee in it for the start of a ride.
On a tour I do not bring powered energy drink mix but for long rides where I start and end at home I may use powdered energy drink mix for some of the calories, I mix it to half the strength that the instructions call for.
If I am traveling alone, I try to stop for no more than 5 minutes each time I eat, any longer and it is pretty hard to get going again. But when traveling with others, the amount of time stopped generally is determined by others.