Choose the best time for shopping whenever possible,
not when you are both tired.
Include your toddler in the process as much as possible.
For example, they may help count the apples into the bag,
or place (non fragile) items into the trolley for you.
A small bottle of water and a tiny box of sultanas can ensure
your child has a healthy snack. If this is all you offer
from the first shopping trip, it will become part of the routine,
rather than a battle for other food items.
Speak pleasantly to your child. If you whine at them,
they will whine right back.
Be encouraged, as you work on training your child in patience
and self-control at home, each trip will get easier.