The author uses hyperbole on several occasions to demonstrate the magnitude of the situation. He often has the BFG exclaim and confuse words together in his surprise or panic about something. He most clearly uses hyperbole when Sophie still fears the giant and hides in her blanket.
"The wind rushing against Sophie's face became so strong that she had to duck down again into the blanket to prevent her head from being blown away" (20). Sophie's head would not really be blown away - she is simply exaggerating in order to communicate the strength and fierceness of the wind from the giant's running. This example of hyperbole helps illustrate the depth of Sophie's panic. She is so afraid that every moment seems dramatic and strong. It also serves to enhance the strength and menace of the giant. As Sophie is being abducted from her home, everything is heightened.
Another example of hyperbole is "The houses looked bent and crooked, like houses in a fairy tale" (10-11). The houses that Sophie and the BFG pass on their initial journey to giant country look crooked in Sophie's imagination. She uses hyperbole here to illustrate just how quickly the giant is traveling with her. By imagining this picture, the reader is better able to imagine how fast and how scary this journey must be for Sophie.