In The BFG, the BFG has a drink that is similar to soda pop—but what is it actually?

In Roald Dahl's story The B.F.G., which is about a Big Friendly Giant, the BFG in question enjoys a drink called "Frobscottle." Frobscottle, he says, is a fizzy drink (this is what seems similar to soda) in which the bubbles sink instead of rising (which is the opposite of soda). The little girl in the story, Sophie, is quite worried about the implications of this. She thinks that if sodas have bubbles which rise and...

In Roald Dahl's story The B.F.G., which is about a Big Friendly Giant, the BFG in question enjoys a drink called "Frobscottle." Frobscottle, he says, is a fizzy drink (this is what seems similar to soda) in which the bubbles sink instead of rising (which is the opposite of soda). The little girl in the story, Sophie, is quite worried about the implications of this. She thinks that if sodas have bubbles which rise and make a person burp, then this frobscottle's bubbles and their sinking will cause a much worse bodily reaction. The BFG is very excited about her realization, and announces that giants call that kind of gas "whizpopping," and find great entertainment and enjoyment in laughing at one anothers "whizpoppers." He makes a very logical statement that if celebrities and royal families and everyone else can make whizpoppers, then why should it be considered impolite or, at least, not talked about?