What's it called?

While we were at Yia-yia's house, Julia was playing with a bin of matchbox cars and trucks. At one point, she showed me the following object and asked me what kind of car it is:



I have to admit, I'm not sure what it's called. An army tanker? I certainly know what its purpose is, but I don't know the technical name. Luckily for me, Julia was able to tell me: "Oh, Mama, I think it's an S-O-I-I-P. You know how I know that? Because that's what S-O-I-I-Ps look like." Maybe in her mind it's a variation of an SUV. I, of course, filled in her acronym in my mind, but I won't share it here - I'll leave it up to you readers to create your own.