the sword in the lava ?Ssuke can teleport to the sword I think .
suiton as a water supply would only temporaily help him surviveOr sasuke train and master all jutsu including water element, and master his teleportation and jubi eye
that's actually the most probable approach I could think of so far..Kaguya goes to Sasuke. Sasuke figures out what to do. Kaguya opens her dimension again. Sasuke uses his teleportation inside the dimension. He teleports into her dimension while she teleports to get away and back to the others.