Best fluid. Water - everyone (average 70 kg person) should drink enough water to produce 2 quarts or urine a day: otherwise you are clinically "dehydrated." (actual fluid intake varies between individuals based on activity/climate/exertion/....).
Kidney pain. Best intervention is high fluid intake - 4 liters per day of water, supplemented with lemonade one quart per day and or lemon extract from ReaLemon 4 tablespoons per day. Avoid animal protein. Avoid animal fats Take in more plant fats. Avoid simple sugar. Eat complex carb from colored fruit and vegetables.