Actually, dont worry about how much sugar is actually in the fruit. As long as it is decent high quality fruit you will be fine. I feel like there is a natural fear towards high "sugar content", honestly unless your a type 1 diabetic dont go crazy over worrying about sugar content! Dont forget you can juice veggies too if you have the desire too, and switching between fruit and veggies would help reduce your overall amount of sugar content throughout the day!
Also I dont know what kind of diet changes you are making, but a multi vitamin also helps you with general overall health. Although you could possibly get checked for vitamin deficiency for certain things and then you can take specific vitamins, as if you are deficient in certain vitamins, a multi will not have enough of that certain one in it to bring those deficient levels back up.
I personally like to try different things, for example I have recently been reading that the vitamin/mineral Chromium is extremely helpful in insulin resistance and therefore because I am a type 1 diabetic, have decided to start taking a dose of chromium.
I find the real beauty of vitamins is that it is pretty hard to overdose on them, most vitamins it would take you a LOT to even get any awful side effects. Ive heard of certain Vitamins (such as C and D) being dosed in the 100's of thousands of mg and still barely any side effects. That would be given intravenously but still, as you can see ... it really doesnt hurt to try a couple vitamins...as your body needs that too.
If you are not willing to take vitamin products the other natural way to do it is through food! Start looking into healthy foods, raw/whole food diets are very good because they focus on uncooked foods which therefore preserve the vitamin/natural enzyme content of the product.
I believe its something like anything you cook above 112C kills off most if any natural living enzymes and also causes anything else important to our bodies to be destroyed.
EDIT: Also, depending on what kind of food you are currently intaking...if you intend on detoxing, beware your body can react differently, such as skin breakouts (acne, skin rashes etc) as well as other things, so dont lose hope but just remember that the first couple of days (or weeks) may be tough...
Also, if you are looking to improve health, reduce if not eliminate all pop and fruit juice intake (I use a bit of fruit juice for smoothies but thats it). Also dont forget starch is another biggy, if you can help it try to reduce starch intake and increase your protein intake!
Sorreh, late night rant
cant sleep tonight!