What I do and what seems to be generally accepted is to wait about 1 hour after eating or take it on a completely empty stomach.
I think you could eat about a half hour after taking it but I would think longer would be better. I usually took it in the evening only but I did occasionally take it earlier in the day also, with the lower doses, and this was between meals.
Eating sooner after it may settle your stomach but I never got nauseus so I don't know myself. If you eat straight after it's going to be likely to reduce it's effectiveness even if theres no C
Do you mean you add citric acid to the juice after you've activated it?
You have to activate it with the citric acid or lemon or lime but you don't have to add anything else but the juice and or water