First, you dont want them to see the outside because it can be scary so best to put a cover over the cage. Make sure they have lots of things to entertain them and food/water. Most important, if usally its silent in the car make sure you put music on so they don't be scared. Good luck :D

You can put plenty of food and water in the cage and leave them alone rather then stressing them out for a 6-7 hour round trip drive.

I have left mine up to a week and they were fine.

I'm going to the beach for 3 days and I can't leave my parakeet behind. What's the best way to have him in the car so he won't be stressed out. It's a 3 hour drive. He's not really scared of anything he always chased the dogs around and they run and hide.