Heres a quick how to "Rotten Bunny" Burrito.
I have used this method for nasty cats for years.
This will all be done with your rabbit on a table, and you behind them.
Get a thin towel, you will want there to be a few extra inches infront and behind your bunny of the towel.
Place bunny in the center of the towel faceing away from you. Lager edges of towel will be infront/behind bunny.
Bring the front of the towel over your bunnys paws, and under their chin, up to their neck, fairly firmly.
Grab the front corner of the towel and tuck it in. Being sure to be careful, but keeping tension on the towel around the neck
do the same with the other side. The entire towel should be somewhat snug around the bunny and you should only be able to slip a finger between the towel and your bunnys neck. You want this to be tight but you do not want to harm them. At this point you will now be leaning over onto your rabbit, kind of squish them between your chest and thet able, they should not be able to back out because now youre in the way, and youre in control.
Their legs will be totally enclosed, they should NOT be able to slip their front paws through the neck hole.
Using the palm of your hand, place that on the top of their skull and grip their head, use your middle and ring finger and place those on their jaw bone, NOT the fleshy part in the middle but directly on the bone. You should have a fairly firm grip on their head but at the same time do not be too rough. Use your index and thumb to lift their lips. They should not be able to move their head while you are doing this. Quickly stick the syringe in there.
This is all happening while you are ontop of your bunny (NOT SQUISHING THEM)
Give it a try.
Had to make sure her bunny was okay after all that, phew!
She let out quite the thump when she hopped down to the floor.