Is that something your vet recommends – medicine via water bottles? It really wouldn’t ensure that they get the meds as they can go off food and water. A spay op is pretty invasive and females recover more slowly than a buck may from a neuter. Generally, you should be given pain meds to take home that are given by mouth via a syringe (like baby meds.) They main things post op is to check their incision, prevent them pulling stitches, pain management and ensure they start to eat and drink so as to prevent a gut slowdown.
This is from the House Rabbit Society on per/post op care.
What pre- and post-operative care should one give?
Give the rabbit acidophilus for a couple of days prior to surgery, just to be certain that the digestive system is functioning in fine form. Don’t change the diet it any way during this time.
After the surgery, continue giving acidophilus until the appetite has returned to normal.
Inspect the incision morning and evening. After a neuter, the scrotum may swell with fluids. Warm compresses will help, but it is nothing to be overly concerned about. With any sign of infection, take the rabbit to the veterinarian immediately.
Keep a newly spayed female away from all male rabbits (neutered or not), as serious internal damage can be caused if a male mounts her.
After surgery, keep the environment quiet so the rabbit doesn’t startle or panic, don’t do anything to encourage acrobatics, but let the rabbit move around at her own pace– she knows what hurts and what doesn’t
Some veterinarians keep rabbits overnight. If your veterinarian lets you bring your bunny home the first night, note the following:
Most males come home after being neutered looking for “supper”– be sure they have pellets, water, and some good hay (good, fresh alfalfa is a good way to tempt them to nibble a bit)
Most females want to be left alone, are not interested in eating at all, and will sit quietly in a back corner of the cage (or wherever in the house they feel they will be bothered the least)
The following morning, or at latest by the next evening, it is important for the rabbit to be nibbling something. It doesn’t matter what or how much, as long as she is taking in something, so the digestive tract won’t shut down. If she isn’t, tempt her with everything possible, and as a last resort, make a mush of rabbit pellets (1 part pellets, 2 parts water, run through blender thoroughly, add acidophilus, and feed in pea-sized bits with a feeding syringe through the side of the mouth)
Occasionally a female will pull out her stitches. Get her stitched up again, and then belly-band her by wrapping a dish towel around her whole middle and binding that with an elastic bandage wrapped snuggly over it. If she can breath normally, it isn’t too tight.
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