The best replacement for inhalation is exhalation.

The best alternatives to inhalation are rated as following:
★★★★★  exhalation
★★★★  inspiration
★★  aspiration
★  insufflation
★  ingestion
★  intravenous
★  injection
  nebulization
  sterile water for irrigation

Your alternative for inhalation is not listed? Suggest!
Speaking about inhalation, one probably shouldn't forget about essential oils.

Other search terms related to inhalation and their ratings are:
★★★★★ essential oils
You have in mind a companion for inhalation and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of inhalation in all years. Click on graph for more.
inhalation
exhalation
inspiration