For exam 90, its quite easy with fire main, since main can keep sasori asleep. If sasori uses his mystery, this fight becomes near impossible to win, since he will keep reviving and others will hit hard.

If you still have fire, I'd suggest to try the method in this thread:
http://forum.naruto.oasgames.com/en/forum.php?mod=viewthread&tid=346&extra=&page=28