For such a flavoring, I use either a 1/2in or 1in 24-gauge blunt needle with a 1ml syringe.
Someone said they used a 27guage needle for those, but I found that gauge to be too small - takes forever to suck any out at all.. 24gauge is likely the smallest I'd personally use.
Also consider using a glass syringe. The 1ml ones I get from Northern Technology & Testing have finer gradations than the 1ml plastic ones - .02ml gradations, IIRC (or maybe .002ml, I forget ATM). And the gradations don't wear off. Plus they don't melt and get stuck due to those plastic tank-busting flavorings like some fruits or mints.
The glass ones are more expensive (starting at ~$12 IIRC), but they should last forever provided you don't break them - and wash and
thoroughly dry them (else they get stuck, requiring a hot tea kettle).
Over the years, I've amassed a fair collection of them: three 1ml ones, a couple 2ml ones, 1 5ml, 1 10ml, and 1 30ml. I ended up getting the bigger sizes to measure the PG&VG, as I've been discovering the plastic ones will become unusable after a while - the plastic/rubber plunger starts getting stuck. Plus with the glass ones, you don't have to wrap tape around them to preserve the printed gradations - but you do have to get used to the finer & odd gradations with them.
I ended up using tape over a tiny label to remind me of the gradations on them. .... And make sure to keep the sets together - the glass-plunger and syringe parts are numbered just for that purpose.
Just collect one at a time if need be.. That's the way I did it.. There didn't seem to be any shipping discount if ordering more than one, anyways.