Do you use both exists to the driveway? If not you could close one end off.

You could put up a nice sign stating it is private property no trespassing.

We are on a private road and put up a sign and it works for keeping cars out . Ours dead ends though. It cost $ 50.

You could put a speed bump at each end of the driveway. People hate speed bumps.

Could you narrow the entrance (with potted plants, or similar) to make it look less inviting. Or temporarily park somewhere that blocks people from driving through?

spike strips.

Are these the cars of neighbors or do you even know? If you know who they are, you could do the neighborly thing and politely ask them not to drive through your driveway because it's not a street.

Orange traffic cones, they sell them at Lowes or Home Depot. Without seeing pics, that's my cheap solution, or just get rid of the connection to the main road.

In my neighborhood, the cut through traffic would be Amazon delivery drivers and talking to them would be useless. I'd place a couple of large planters on the cul-de- sac end of the drive.

@queenmoomba - could you post a photo or a sketch of the area? I'm having a difficult time envisioning this. You said that people are using your driveway "as a cut through when I don't park in my garage." If you're not parked in your garage, aren't you parked on your driveway? If so, how can other folks be using that driveway? Or are you parked at the curb on the street, leaving your driveway open and accessible?