I wouldn't try to correct his word, I'd just redirect him so he thinks healthier drinks like some juices are soda too and that "soda" is just another name for drink. There's plenty of time to fine tune his language when he's older; it's not like "soda" differentiates between orange, grape, or cola flavors, etc. I'd give him what you want him to drink and tell him it is soda; let him be a bit unhappy in the inaccuracies of the language for a bit :-) Just make sure you're not drinking "soda" when he decides he wants some! Wouldn't hurt for you to give it up to He'll copy you and want what he sees you're drinking.