The first few days of  k2 base camp trek till Urdukas we have access to fresh running water, you can wash and shower till Urdukas camp.  Ahead of Urdukas camp, the weather conditions do not allow to take a shower until back to Urdukas or Saicho.
We would have portable showers throughout the trek, you can ask the guide for the shower or to warm water if you need to take a shower.