Soaking fruits in fruit juice [closed]

Yes you can, but I'm guessing you want an esthetic effect somewhere in your recipe... maybe using the juice somehow as an after glazing effect or something like that? Post your true final purpose :)

Can I soak fruits in fruit juice for a fruit cake?

The short answer is yes, if you mix different fruits in different juices the flavor will most likely be confusing but overall, expect it to be sweet.

If yes, do I need to boil the juice?

If the juice is fresh (from a can or a box that you just opened, or freshly pressed juice from fresh fruits) it does not need to be boiled, unless you want to cook your fruit before integrating them to the cake. Of course if the juice isnt fresh you should not use it.

Boiling fruit juices could result in loss of liquid and you might not want that. What is it you're trying to accomplish ?