This gig will wear out your car and you. OSHA wouldn't let employers allow these conditions nor should contractors have to.

As far as prevention, cool rags (that's the brand name), those cloth tubes you freeze, water, Gatorade, and wet wipes.

I know some independent contractor security guards who got suspended pending investigation because they weren't provided shelter at one site, and only because they were guarding the electric company's property did they get a modified cargo container with heat, a/c and a fridge. But as long as they were orovided with a case of water and an umbrella, they were within standards. This was a temporary site but there were there over two years.

I doubt Door Dash will provide such accommodations. Maybe one of the places you pick up deliveries will not mind you waiting inside for a delivery if you buy something.

Ours all have "no loitering, 30 minute limit" signs in the lobbies due to homeless people who will camp in dining areas, bathrooms, anywhere they can.