Steve Brezenoff 
I Dare You! [PDF ebook] 

Gutters, Tad, Kayla, and May are in a club called the Braves. They take turns giving each other dares. This time, Kayla is dared to sleep over inside a creepy old house. When her friends show up the next morning, Kayla won’t wake up. She’s still alive, but poisoned, and in a coma. A piece of paper nearby is marked with one letter, K. Is someone trying to kill Kayla? The remaining three Braves will have to find out who’s after their friend.