Now, this scene is pretty much the same in the books but there are a few minor differences. The first being that it takes place at a Dairy Queen. Why not a DQ in the film adaptation? Probably due to licensing. The second difference is that the girlfriend is lactose intolerant in the books. Another ailment that Jake himself carries but he projects onto the characters of his story.
Lactose intolerance comes into play multiple times throughout the book, but in this instance an Oreo Brr would be completely out of the question. So, the two opt for Lemonades, one strawberry and one regular. Everything else is largely the same, even the mention of varnish and the melting desserts prompting Jake to drive to a local high school.