when we had a car, our average was 20 minutes, but we would typically be out for many hours.
so, the situation is such that we would keep trail mix in the car, bring water bottles with us everywhere, and also pack a lunch and "wet" snacks (fruit).
but, the reality is that we would drive 20 minutes from home to store, then do the store, and then perhaps--if the timing was right--sit at the little park near the store and have a wet snack (cheese, apple--for example). or if it was lunch time, we would have a picnic lunch.
i had places where we would stop regularly--near play grounds, green spaces--that had tables in the open and under pavilions so that we could eat "out" whether it was raining or not.
A typical day for me in the past was this:
7:00 am--after breakfast--all of us would get in the car and i would drive DH to work. that was usually 30 minutes.
7:30 am-- we would go to the park (usually Valley Forge about 5 minutes from DH's work) and I would potty my son, wrap him, and go for our hike.
9:30 am-- during the hike, i would potty my son, and then we would arrive back at the car around 9:30. i would potty him again, and then we would have a snack. I would set us up on a picnic table either in the open or under a pavilion. we would snack for about 30 minutes. sometimes DS would nurse.
10:30 am-- potty my son again (or he would have signalled already or what have you), and then he has free roaming time or we are at an activity. typically, it was free roaming time in the park. so, he would play.
11:00 am-- this is about the time my son would get sleepy. i would potty him and then put him in the car seat. drive home 20 minutes and he's asleep. bring him out of the car, with our lunch/snack box.
12:00--make lunch for myself at home, son still napping, so i do my daily chore, straighten up, go online, enjoy myself, read a book, cook, whatever.
1:00-1:30--DS wakes and i potty him. then i feed him his lunch, and he has naked time and play time in the house, reading, and if he wanted to, we would dress and he could play outside. snack time in there too.
4:00-- get back into the car to pick up DH, drive to his work and arrive around 4:30.
4:30-- potty my son at DH's office, DH gets into the car with his stuff from the day, drive home.
6:00 dinner time
7:00 bath time
7:30-8:30 evening routine to DS's bed time
8:30-10:00 adult time.
Once a week, morning activity included cleaning the car, rather than hiking.