I use treats to get meds into my girls, which I suppose only works if you just have a few hens. Powder meds are easy to provide on a slice of cherry tomato or a dampened piece of bread and I give liquid doses soaked into a piece of dry bread. They wolf it down!
The only drawback is if you have very dominant hens who barge the the other hens out of the way or steal food from other beaks and end up double-dosed!
I've tried syringing meds into beaks and far more goes onto the floor than down the throats. I usually have no idea if I've given them enough. Similarly, water soluble stuff is a bit hit and miss - if they are poorly they have usually reduced their intake of water and food, so you don't know if they're getting enough. In that case I tend to 'dunk' the heads right under the water - they hate it, but it forces them to drink.