The texture doesn't really bother me but the taste is sometimes not fantastic. So I've said to him to start drinking more water (he doesn't drink water a lot anyway so it'll be better for him than always drinking fizzy juice) because I've heard that can improve taste.
I could see upping the ammount of water would dilute it somewhat, and cutting out fizzy drinks is never a bad thing..
On the up side I'd heard that pineapple juice was quite good for improving the flavour, so you could maybe get him on that instead of so much pop.
There are some foods that improve taste to, so maybe someone here will know, or if no one steps forward you could maybe google it.