Or take out their supply lines?
It's getting very cold there, conditions are appallingly bad in the defensive positions by all accounts, and Ukraine has shown significant skill in being able to knock out logistic supplies in the past. Coupled with what seems to be far poorer morale amongst Russian forces, and the inevitable slow down of any advances on the ground as winter sets it, that has to be a tactic that might give Ukraine the nest bang for the buck, with the least loss of life. Depends how good Russian AD is in that region, and whether Ukraine can effectively defeat it.