Park safely and keep the dog secured before opening a door. Do not chase them from seat to seat or pull them by the collar. Check whether the step down is high, the surface slippery or the destination worrying. A dog who cannot move comfortably, seems weak or shows pain needs a veterinary assessment rather than another lure.
When safe to do so, attach a short lead to an appropriate harness while the car remains closed. Keep traffic, dogs and people away from the opening. If you cannot get the dog out safely, stay with them and call your vet immediately for an exit plan. Never leave them in a parked car. If the cabin is hot or the dog is overheating, seek emergency help now rather than trying another treat or training step. The car-travel article on nausea helps if drooling or vomiting is part of the pattern, but fear of the step or destination needs its own check.
On a day without an appointment, practise from a parked, cool car in a quiet place, letting the dog choose a manageable movement toward the exit. A suitable ramp or stable step may help a dog with mobility limits after a vet or professional assesses fit. Never make the dog leap from a height to earn a treat.
Today, identify the next destination and a safe exit path before starting the engine. Getting out calmly matters more than proving they can jump.
Sources: Dogs Trust on gradual car travel and safety, VCA on secure car travel, VCA on pain-related changes.