There are 1 ml glass vials I use for designing flavors. That's plenty to drip and try out an idea. What prevents most people from doing that is that they are limited to droppers to measure out flavors, and 1 big drop is around 0.040 to 0.050 ml, or 5 %, not a very fine brush to work with. I personally think many people use too much flavoring, since we don't know how safe they are to inhale, it's safest to use as little as possible. If you get some insulin syringes with 32 gauge needles, they cost about $3 for 10, you get drops of about 0.0025 ml out of them, so it takes 4 droplets of flavoring to make 1%, which is more like it. They have some fine-tipped pipettes on e-Bay at $6 for 50 shipping included that make 0.012 ml drops. You can always calibrate a given dropper by counting droplets to make e.g. 1 ml. It's delicate cleaning off the needle/tip not to cross-contaminate flavorings, then pulling up just a hair from the next bottle, then pushing out these micro droplets, but well worth the trouble, since a lot of flavors make a big difference well below 1%. Once you have the percentages worked out, you can make a 3 ml bottle to try. Finally I make 10 ml ones to use, they are handy to carry.
