South Location: The closest possibility to buy food is in Hella, which is a 25 minutes drive away. There is a grocery store (Kjörbudin) and a petrol station. The petrol station is open until 23.00 every day.
If you want to get alcohol there’s only one store chain in Iceland. It is called vínbúðin and is closed on Sundays and holidays and also closes at 18:00 every other day. The closest of these stores is in Hella.
West Location: We recommend stopping in Borgarenes to get grocieries, there is a bakery, a Bonus and a Netto store. If you are arriving late, the N1 petrol station is open until 21:00.