Just wondering, why don't you exhale through a tissue, hankie, napkin, sleeve, anything cloth. The water vapor will collect in the cloth, no vapor will be seen.
Ah back in ye ol college days we made "poofs" which was a bunch of fabric softener sheets stuffed in a toilet paper roll tube. That helped with the ciggy smell too. But we don't have to worry about smell (unless you have a strong flavored juice, but that smell dissipates very quickly)
So, I dunno, empty out a Sharpie pen, or a marker, some fat pen-like think. Stuff some TP or napkins in there. Tada, your exhaler.
And just make sure your drag in takes it all in & resist the urge to blow smoke rings.
Oh, this should also help with smoke detectors. Most detectors work on the process of particles interacting with them. When smoke is in the air the air is crammed full of tiny particles (that gross yellow stuff on the inside of your car windshield, or the stuff collected in your analog cig filter) These particles will either collect on a plate inside the smoke detector, disrupting an electrical connection, or collect on a plate and block a beam of light. This then activates the detector alarm.
I am a theater artist, and I can't tell you how many times fog machines (that use PG/VG) set off smoke detectors. Because the PG is broken down to fine particles with water, the smoke detector doesn't know the difference. It just sees particles.
I get worried that the smoke alarm will go off at work (sometimes I vape in the bathroom when it's too damn cold outside) This prevents that from happening.
Peace.