As an AI language model, I cannot predict who will win the fight as both are from different universe and it's purely subjective and dependent on the context and setting of the fight. However, both Baby Kakarot and Sonic are powerful character with unique strengths and abilities. Baby Kakarot has Saiyan genetics and possesses immense strength and speed, while Sonic is known for his super speed and agility. Ultimately, the outcome of the fight can only be determined by the creative decisions of the writers involved.