They swap Katie's clothes

Sydney and her hench-girls got to work. One girl pulled out a seam ripper. Sydney herself drew a small tube of water soluble glue. With the seam ripper the girl quickly shredded every seam in Katie's sports bra and spandex shorts. Next Sydney carefully glued the seams back together. When they were done the clothes looked untouched, but were now extremely fragile and would fall apart with much contact with water.

Giving Monica the clothes bag She hurried into the room. Katie was still showering. Perfect! She went over and set the clothes back down, then hurried away. She found Sydney and the others outside. At the same time the unwitting Katie exited the shower, and began dressing in the clothes that she was unaware had been tampered with...