You won't be able to make lava flow through the sugar canes.
Steps to reproduce:
#1. Go to a lake or just place sugar canes near water.
#2. Place lava near them notice that they will go to different directions.
#3. Bug found!
MCPE-9230
Sugar canes unable to get deleted by lava
Resolved
Works As Intended
0
(Unassigned)
Unconfirmed
Phone - Android - Huawei Ascend
Android 4.4.4
0.11.0, 0.11.0 Beta 14
Retrieved
Works As Intended. Sugar canes should be unaffected by all liquids.
I recommend checking the Minecraft Wiki prior to reporting an issue on the bugtracker, as what seems to be a bug to you may actually be intended.