香香 is a reduplicated form of 香 (xiāng, 'fragrant/delicious/sound sleep'). As a reduplicative (r.f.), it adds a lively, colloquial tone. It's used in two main contexts: describing food as delicious (often in child-directed speech or casual compliments), and describing a deep, satisfying sleep (睡得很香). The reduplication softens the adjective and makes it more vivid.