We use warm water in a 1 L graduated cylinder. (You know, what you'd empty an adult Foley into?) Don't worry, we don't use the same one as for the Foley! They have a dedicated one for warming feeds, changed weekly. We keep the syringe in the sleeve it came in while warming.
We use the Medela waterless breast milk warmers. They also can turn frozen milk into thawed milk or warm milk depending on what you want. It holds bottles and syringes of all sizes. We really like them a lot.
Styrofoam (sp?) cups changed QD, with the syringe cap on and place back in the wrapper or in a glove. We tried the penguin system and the medela. Those bags are expensive and the other took too long to warm up. We have to have something over the end d/t crypto (? some micro bacteria in our water/sink) Or if its a trophic put it in the giraffe while Im doing my assessment.
Also will use 1L graduate container with lukewarm water and place capped syringe in, or some RNs will place capped syringe in a glove or ziploc baggie and place the waterbath. Graduates are changed weekly.