DiasMumma-
After reading your post, my thoughts were (and I have been in your position)- just don't have any beverages but water in the house for a while. Calcium fortified juice is inferior, anything "fortified" is lacking the nutrient complex that only nature can endow a food with, a whole food not processed (juiced, concentrated, pasteurized, etc)... I don't think you need to worry about it so much, I believe the good feelings you maintain with your daughter will be more important than regulating what she eats/drinks- which will probably only create an unhealthy attitude in her where food/drink is about control. The idea you expressed about "outsmarting her" too, I think will diminish the quality of your relationship, in that it places you at odds in a way...
And on the topic of two year old tantrums in general-
I am loving them! I have opened myself up to my 2 yr old in a way that I no longer choose to perceive him as defiant, stubborn, or anything negative- he is, developmentally, having a very difficult time integrating the wild world of emotions and thought in his very small, very inexperienced body! How frustrated would I be if I were so small and all the bigger people around me seemed to control so much of my life, extinguish so many opportunities for self-expression and exploration... loving him through it and helping him find the HUMOR in life are what keep us connected. Yesterday as he threw himself on my feet screaming and flailing while I did dishes because of some mishap, I told him I was afraid little monsters had grabbed hold of my feet- they might BITE me! And this struck him as hilarious and he tried to bite my ankles, so I ran around the kitchen running from the feet biting monsters until he caught me, threw his arms around me and gave me a bear hug. Not to suggest that will work with all children- but I think most of them have a personality bent which makes a certain approach work well and we must just be detectives... with this child of mine, humor is it... during this difficult part of his life we go out less often, I even find that my own concern for my self-image (what other people will think of how my children behave) hurts my ability to mother them to my greatest degree- so we don't go out much! We are happier that way, we consume less, it is just for a time. Embrace it- it is such a fascinating part of watching your child grow and I swear, the first time around with DS1 my reactions to him were frustration, opposition, battle of the will, "you will not get your way"- all of which contributed to very negative dynamics in our relationship that I hope I will be able to work through, they are still not resolved- he is passive-aggressive and obviously does not trust me to provide for his needs. DS2 is in love with me, always wants to be with me, do chores with me, believes I can meet every need he has and make any booboo all better, it is just so different and wonderful to embrace him, tantrums and all, to accept him as wonderful and not simply "being tolerated through this stage"... ultimately, if I was going through a rough patch- depression, anger, feeling overwhelmed, feeling afraid- I would want someone to cherish me and remain optimistic yet empathetic... if I felt they thought my life stage was a burden/frustration to them, I would automatically be less inclined to trust them with who I was, to feel at odds...