I can weigh in on this. Is the Sonic your only car? My wife has a camry which is nicer for baby duty if we need a lot of stuff but around town I try to use the sonic since it gets better gas mileage.
I attached two pics to show you different ways of putting it in the hatch.
Very few strollers will fit with the "deck lid" if that's what you would call it on the hatch, because they are too long and the sonic isn't wide enough to accommodate them. I like to folder down the driver side rear seat and take the deck lid off and just use that area for storage. Once my son is forward facing in the car seat I'll probably switch it around but for now I need the leg room since my wife is shorter than me and I'm 6' tall.
The other option is to take the deck lid off and leave both seats up and let it stick above where the deck lid was.
I have three strollers the one in the picture is this one.
Amazon.com: Mia Moda Facile Stroller, Tangerine: Baby It stays in my car pretty much all the time. My wife keeps the fancy stroller
Amazon.com: Baby Jogger City Mini Single - Black/Gray: Baby in her car since she has my son more than I. The city mini will actually fit with the deck lid down if you play a mean game of tetris. I don't think very many other strollers would I looked at a LOT of them and this was the only one that I think would and I didn't want to spend that much on another stroller and my wife won't let me have the fancy stroller in my car and I'm not spending $250 on another one.
Jogging stroller: We also have a BOB SE
Amazon.com: BOB Revolution SE Single Stroller, Black: Baby it will fit easily with the seat folded down. I haven't tried to fit it with the seats both up. We don't use this one much unless we are going somewhere like the zoo. It mostly just gets used as a jogging stroller right out of the front door.
If you have any other Sonic baby questions I'd be happy to answer them if I can.
Congrats on the baby! :banana: