I can't remember if they were exactly the same or not...but you may like to know that at Boma it was included in the price of the buffet and you could get as many refills as you like. At Tusker House it cost extra. Just so you're not surprised if your waiter doesn't mention it.
In December I had 3 or 4 glasses of juice at TH and it was included in the buffet - no extra charge
Juice should be included in the buffet price whether it's lunch or dinner because your buffet includes 1 non-alcoholic beverage.
Maybe ordering coffee with the meal (in addition to the juice) would have the server charge for an extra drink?
I wasn't included at dinner for us either. You could only get soda or water. All of the juices were extra. I wasn't too happy about it and I did complain because at that price they really should include the non-alcoholic drinks. It seems that each restaurant does it differently.