Why not - just make sure you're ready to handle the toddler sugar rush afterward! Haha. But experts say to give the hot chocolate sparingly, and actually to wait until your kid is 2 years old, as chocolate does contain some caffeine that can make it harder for your toddler to sleep.
I never gave my boy chocolate milk till lately. He is about 3 years old. I keep his drinks limited to water and milk.
I tend to avoid all those health drinks or chocolaty flavours. My 3.5 years old has recently started with some Milo.
I would say 2yo is ok! Just make sure it isn't too sweet.