Whatever turns (one) on American British informal
Said to imply that one can do whatever they feel excited or pleasurable
James: "Is it okay if I turn on loud music?" Marry: "Of course, whatever turns you on."
Kathy: "Such an adorable puppy! Could I pet the dog and ruffle its fur." Adam: "Whatever turns you on, Kathy!"
Today is my birthday, so I can do whatever turns me on.
Meaning absolutely certain or without a doubt
I am as sure as God made little green apples that Peter's the one for you, you two make a beautiful couple.