I currently have 1ml, 3ml and 20ml syringes I use while DIY. I typically have a 14 or 18 gauge blunt tip needle to get the flavoring out of the bottle, but sometimes have an air bubble or pocket in the syringe. The first time I ever used the syringe I had no problem using the plunger on the syringe to push the juice back into its original bottle to get rid of the bubble, but in between flavorings, i rinse the syringes out. I rinse them well, but really dont want to cross contaminate my flavorings. Is there a better way to do this? In the medical field, when filling a syringe with a hypodermic needle on it, you do it upside down, but the bottle is sealed with a rubber top that the needle pierces with each use for no spillage, obviously I cant do that in this situation.