DIAGNOSIS New filter carbon media needs a proper extended flush, or the polyethylene tubing is leaching taste because it wasn't flushed separately.
FIX Flush the system aggressively. Run cold filtered water continuously for at least 10-15 minutes into a bucket, not just a few gallons. If the taste persists, disconnect the tubing from the faucet and run water directly from the unit's outlet into a bucket for another 5 minutes to flush the tubing itself.
IF THAT DIDN'T WORK Check that you removed all plastic shipping wraps from the filter cartridges before installation. A retained wrapper will cause foul taste.
HEADS UP If you smell sulfur (rotten eggs), that's bacteria in the filter—you need to sanitize the system with a bleach solution per Aquasana's protocol and replace the filters.