Sealed disposables cannot be opened or refilled, so internal cleaning is not possible. You can still clean the part that touches your mouth, which is where hygiene matters most.

Use a cotton swab lightly dampened with warm water or 70% alcohol to wipe the mouthpiece, then let it dry. Do not drip liquid into the airflow opening, because moisture can short the sealed battery. Given the mouthpiece contamination findings, a daily wipe is worth the 10 seconds.