[TOMT] (BOOK) Children’s book, possibly titled “Ketchup!”

I vaguely remember reading a children’s paperback at primary school, some time between 2001-2004. For some reason I believe it had “Ketchup!” in the title, though I don’t remember the relevance to the story. I may be mistaking it with another title. The cover was illustrated and stylised, featuring a boy doing a trick on a skateboard or a bicycle. I recall the story was based in a derelict, impoverished or possibly post-apocalyptic setting and featured a cast of poor children who hung out in a skate park. I think there was mention of a flood or some kind of disaster. It’s been tickling my brain for a while and would love help finding this weird, bleak little book.