The Red Cross was allowed to visit Terezin once. The village of Terezin was spruced up for the occasion. Certain inmates were dressed up and told to stand at strategic places along the specially designated route through Terezin. Shop windows along that carefully guarded path were filled with goods for the day. One young mother remembers seeing the bakery window and shelves suddenly filled with baked goods the inmates had never seen during their time at Terezin. Even the candy shop window overflowed with bon bons creating a fantastic illusion she would never forget. Source.
In fact, these sinks were built solely for the Red Cross visit and were never actually used by the prisoners at Terezin.