Plastics often retain water. Use a rinse agent.
FIX: Fill the rinse aid dispenser with a high-quality product like Cascade Platinum Power Dry Rinse Aid or Finish Jet-Dry Rinse Aid. These are designed for great drying action and to protect against spots and film on dishes, glasses, and plastic.
IF THAT DIDN'T WORK: Check your cycle selection. Some cycles have a heated dry option. Also, load plastic items on the top rack where the heating element's effect is less direct, and angle them so water can run off.
HEADS UP: Only wash plastic items marked "dishwasher safe" or the equivalent. For items not marked, check the manufacturer's recommendations.