Here's a link to a video on You Tube that shows how to mix critical care and how to syringe feed a rabbit:
[ame=http://www.youtube.com/watch?v=8iGZVYVm5Bg]http://www.youtube.com/watch?v=8iGZVYVm5Bg[/ame]
The tip of the syringe is placed in the gap between the molars and the front teeth. When the syringe tip is in place, most bunnies will begin to chew, so squirt slowly while the bunny is chewing. Don't place the syringe deep into the mouth or squirt too quickly, or the bunny could aspirate.
If you don't have critical care, you can soak rabbit pellets to soften them and make a similar consistency.
If you don't have a syringe, you may be able to ask for one at a pharmacy or find a curved tip monoject syringe at a craft store (like Michael's). Here's a picture of the curved tip syringe:
http://www.vetdepot.com/syringe-12-cc-curved-tipped-monoject-one.html
The tip is quite narrow, so you would need to cut it back about half way.
You can also syringe feed baby food- plain carrot or squash work well. Make sure that it is just plain carrots or squash- no sweeteners or additives.
Plain canned pumpkin can also be syringe fed. Make sure it is plain pumpkin, NOT pumpkin pie mix.
You can also offer the baby foods and pumpkin in a bowl.
Crushed basil can sometimes act as an appetite stimulant. You can chop fresh basil coarsely and crush it between your fingers a bit. Offer the basil itself, some bunnies will eat the basil. Even if the bunny doesn't eat the basil, often the smell will make them perk up a bit and look for food, so offer him some of his favorite greens along with the basil.
When my bunny had a URI, I would put him in his carrier and bring him into the bathroom while I took my shower. The steam would act as a decongestant and allow him to breathe more easily. It's important to keep the shower fairly short, you don't want the bunny to overheat.