I just finished giving a 10 day course of sulfa-based antibiotics to my rooster. These meds taste terrible and even my rooster, who is a happy glutton right now since he's a growing teenager, would turn away any food that I applied it to. I had to give it directly a few times, and you are right, it's a real struggle. Despite this, it's important that your hen get the full course and complete dose each time. To this end, it is a bad idea to offer it in water, because the bird is unlikely to get a complete dose (and may associate the water with the bad taste, and not drink enough). What ended up working best for me was to make an oatmeal and mix in his favorite treats, then use the syringe the medicine came with to 'inject' a little of the antibiotic into bite-sized balls of the thick oatmeal. He ate these without tasting the medicine because he swallowed them whole. This might also work with bread, by balling up pieces of soft bread and putting the liquid into them.
If you can't get her to eat it, it is worth the strife to directly administer the medicine, but please do be careful not to aspirate her. Once her mouth is open, slide the needle-less syringe into her esophagus and administer it. As might be obvious, never use a needle to do this!
Here is a link with photos on how to dose a bird orally. It is a peafowl, but chickens look the same, just smaller. The airhole will look smaller in a chicken. It is always in the center, and looks like it is behind the tongue. The esophagus is to one side (to your left, if you are looking at a chicken head on).
http://www.hopkinslivestock.com/oral_dosing_article.htm