3 choices as I see it:
Glass -- too chancy --bit of expense with no guarantee.
Scale -- May be easier in the long run. (not cheaper)
Do nothing and wash (3 shots/squirts of water from 3 different water containers) the syringe immediately after use. TA (Tobacco absolute) will effect the syringes I use. So, 3 shots in succession, of clean water allows syringe reuse for me.
The problem with the do nothing idea is that when those offending flavorings hit your syringe, they can seize your equipment immediately. I remember a certain banana flavoring I tried--couldn't squirt it out of the syringe once I got it in there. Too late.
I thought about glass syringes, but they're pricey, and I decided it wasn't worth the effort to get THAT exact anyway.
Scale. I have a good one. I make homemade soap. But I discovered mine isn't exact enough to measure drops. Wouldn't move even after 4-6 drops, so I abandoned that idea.
I ordered these and got them today--one milliliter glass droppers I will use for small amounts of flavorings only. Free shipping.
18-400 Calibrated Child Resistant Glass Dropper (7x66)