SandraHi Christine,
I don’t know how old your son is but sometimes when my older boys say they don’t like something I just change the container it’s in and tell them that it’s a drink/snack that they’ve had before and liked and they say "oh, OK". My two older ones are 8 and 5. Unless it has a terrible taste then they usually don’t know that it was the one they didn’t like because of the packaging or because they took a dislike to it without really trying it. Ex... I bought the colored goldfish..same cheddar taste...well my 8 yr old decided that the purple ones tasted gross!! How, I don’t know because when I tried it they tasted the same as the other colors so we had a blind taste test. After a few tastes he agreed that it tasted the same!
In your case, I would try other flavors and maybe give it to him in a thermos or a cool sports bottle. I bet he will find a flavor he likes. Powerade makes some good ones too. Maybe you can buy a few small bottles of a few sports drinks and set up a taste test for him to find one he likes. Have him go with you to the store to pick it out!
Sandra