I find it strange that people allow juice. If the purpose is to get your blood sugar down for a consistent stretch then juice would mess that up. I'd rather it a small high fiber, low sugar snack, like some brown rice with vegetables, than drink an equivalent amount of calories in juice form.
I guess maybe the idea is the juice sugar gets digested quickly and you're back to empty, whereas the rice would stick around. I guess it's a question of whether it's better to go up to a 10 and then back down to a zero, or go to a 4, 3, 2, 1, 0.