Teach dog to jump into car

Hi all! Looking for some tips on how to teach my dog to jump into the car.

She will happily put her front paws onto the car hammock in the back seat, but she won't jump in the rest of the way. I know she CAN do it, she's done it before when I went to pick her up from daycare and she was so excited to see me that she leapt into the car hammock, but I only take her to daycare like once a month when I'm going to be busy for the entire day or something. ​She can also jump onto the couch just fine.

Treats (even things like cheese and yogurt which she LOVES) don't get her to jump, she just wags her tail happily with her front paws on the hammock as yogurt drips off the spoon I'm holding lol! I've tried turning it into a game by running around the car while she chases me and diving into the back seat – same thing, just puts her front paws on and gives me the same derpy smile. I've tossed toys in there. I've played fetch while the back doors are open, have her do a few retrieves outside, and then throw the ball through the back door, and she just goes around the car looking for the ball.

She LOVES the car too, so that's not the problem. Once I lift her in, she'll sit down nicely and let me buckle her in, then she'll either look out the windows or nap until we get to our destination. I've never forced her to put her paws on the back seat, she's always happy to do it because she knows we'll be going somewhere fun.

It's not a HUGE deal if she doesn't go in by herself (which is why I haven't invested in a ramp), she's juuuuust small enough that I can lift her into the car with no problem. She just sometimes gets muddy after playing and I would really, really love it if I didn't have to get MYSELF muddy while getting her into the car!