Diagnosis
This is normal for new units and sometimes recurs if you don't clean the water reservoir and air filter. New plastic needs to off-gas, and stagnant water picks up odors.
How to Fix It
First, clean the entire unit as described above with vinegar. Then, remove the blue foam air filter from the back of the machine. Rinse it under cool water, squeeze it out gently (don't wring), and let it air dry completely before reinstalling. Always use fresh, cold tap water—don't let water sit in the reservoir for days.
If That Didn't Work
Try using filtered or bottled water for a few cycles. Tap water with high chlorine or sulfur content can impart taste. The plastic taste should fade within the first 5-10 batches. If it persists, contact Igloo.
Heads Up
Never use scented cleaners, soap, or bleach in the water reservoir. The plastic will absorb the smell and it's nearly impossible to get out, tainting every batch of ice afterwards.