This might sound stupid I'm sorry but I've had MFLB for quite a while now and I've wanted to clean it and mind you I'm looking at it and it looks really dirty around the mouthpiece because my straw broke like the first day I bought it and I decided to put some minimal hand sanitizer around the mouthpiece and I let it dry for a little like 15 mins and then I took a puff out of it and I tasted some of it in my mouth and possibly inhaled maybe? I don't know if the mouthpiece area gets hot enough to vaporize so I'm sitting here kinda worried I might be in danger? This will probably sound dumb as shit when I sober up.
Isopropanol is not dangerous enough to cause any real damage... Especially in low doses. I wouldn't worry at all.