DEPENDS ON THE STRUCTURE OF YOUR WINE AND IF SWEATING IS WHAT YOUR ONLY TRYING TO ACHIEVE, SUGAR AND THE PROPER CHEMS. ARE THE WAY TO GO,HOWEVER IF FLAVOR AND SWEETNESS ARE DESIRED FEATURES NEEDED TO BE GAINED , THEN JUICE COULD BE THE WAY ,EITHER WAY PROPER SKILLS IN HANDLING THE OUTCOME ARE REQUIRED,IN MY OPINION.
Yep--you sure can. The best juices in my opinion are the frozen concentrates because you can find 100% juice which also boosts flavor. Be sure to add sorbate and some meta along with it.