Have a sweet tooth
Definition 1 of 1
Pro Tip 1/3Figurative Meaning
The phrase doesn't mean one literally has 'sweet teeth.' It's used to express a fondness for sweet flavors. 
Even though she's dieting, her sweet tooth hasn't gone away.
Pro Tip 2/3Not Just Candy
'Sweet tooth' applies to all sweets, like desserts and sugary drinks, not just candy. 
I've got a sweet tooth, so I can never resist a slice of cake.
Pro Tip 3/3Adjective Intensity
Describing the sweet tooth as 'real,' 'severe,' or 'serious' emphasizes the intensity of the craving. 
He's got a real sweet tooth; he can eat a whole chocolate cake by himself!