I was wondering if it's safe to keep aseptic groceries in a hot,
unventilated car for extended periods. Some examples would be unopened
jars of tomato sauce, jelly, bottled water, parmasean cheese,
bread/rolls, and pop tarts. For example, on a camping trip, these
items would not be stored in a cool dry place, but rather inside of a
car. Thanks in advance.

In regards to your question, yes it is safe to store all those items
inside your car.

However, it is not recommended to keep any foodstuffs inside a car in
any campsite in proximity to bears.  Despite the being secured in the
car, the scent is still present and automobiles are not "bear proof." 
All food should be secured in a sealed container and secured off the
ground.

Unopened Parmesan cheese will be fine but may result in a slight
change in texture if stored during a prolonged period of heat.  In
addition, carbinated beverages will expand in intense heat and will
discharge under the slightest puncture.  To prevent this, store food
items in the generally cooler trunk and away from any objects that may
rub against them.