"(Song For My) Sugar Spun Sister" - The Stone Roses
"Sugar Pill" - Ambulance Ltd.
"Sugarcube" - Yo La Tengo
"Sweet As A Candybar" - Air Miami
"Savoy Truffle" - The Beatles

Not about candy the treat but still great songs:
"Candy Says" - The Velvet Underground
"How Does It Feel To Look Like Candy?" - Swervedriver