This is by Lisa Pierson, who is a vet, but it's written for non-diabetic cats:
http://www.veterinarypartner.com/Content.plx?A=3041 With a diabetic cat, I think you would need to have a little less of a "tough love" attitude in terms of some of the things she says about letting them get hungry. (In other words, it's probably not a good idea to be as strict as she is about letting the cat get hungry when they have diabetes, esp if they are on insulin.) Also, please note that if you do get your cat to start eating wet food, you will likely have to adjust the insulin dose. Otherwise, there is a risk of going hypo.
Do you free feed? If you have normal feeding times and do 2-3 meals per day, this will probably work much better. And please don't get discouraged if the below sounds a bit extreme, b/c like I said, my vet had never in 20yrs had a cat as stubborn as mine at switching to wet foods. Major dry food addict! When we first started, my kitty basically did NOT recognize canned food as food or even something edible! Some people also try wetting their cat's normal dry food with water before doing what I've outlined below to see if they'll eat that at first, but mine would not eat his dry food even with a little water (and I was worried about bacterial overgrowth doing that).
First, we went and bought around 30 different brands, flavors, protein levels, etc. of canned food- no joke. Around the times we knew he'd be hungry, we opened several different cans (like 5-7) at once and spread the cans across the floor (I know it's insane). There were pates, chunks in gravy, whole meat pieces in broth, etc. etc. beef, chicken, turkey, multiple types of fish, etc. He did not eat any of them at all. So, if he seemed less disgusted by a certain one (smelled it a little longer, didn't try to cover it up as much, or didn't literally shake his paw at it), we made a note of which it was. After a few days, you end up with a list of like 2-4 that are slightly less revolting to them than the others. Every cat is different (ppl here abbreviate this as ECID)- so your list of possible foods might be bigger or smaller.
Then we bought more of the 2 canned foods he was least averse to, and for his dinner, we started hiding a TINY amount of the wet food in the middle of a mound of dry food at feeding time. By tiny, I mean less than the size of half a pea. Seriously. They can still smell it, so it's best in the very middle of the dry food, all covered up. Very slowly over the course of several weeks, we increased the amount of the wet. If your cat likes Fortiflora or powdered dried liver or bonito flakes, you can coat the wet food in it, or sprinkle the powder on the whole meal as you up the wet food amount. So, while this was happening at dinner time, we were doing something a little different in the mornings for his breakfast.
With my kitty, we routinely feed him breakfast at 6am every morning. So, during the two months that we were trying to switch him, one of us would get up at 5:00-5:30am so that we could offer him wet food while he was hungry, but not delay his normal feeding time if he wasn't going to eat the wet food. So,
if he was willing to try the canned food, he got fed early. If not, we would feed him his normal dry food at 6am. (Once you get them eating just wet food, you can slowly transition feeding time back to when you want it to be.) As the amount of wet food we were hiding in his evening meals slowly increased, we became slightly more likely to at least get him to lick the wet food by itself in the mornings.
That was how we spent the 2012 holiday season. LOL But it was worth every minute of waking up early, etc. in the long run b/c of his diabetes insipidus. There were days I thought we would
never get him to eat canned food
, but after 2 months, he was eating at least some Fancy Feast Beef Gravy Lovers without dry food on it. Now, Gravy Lovers is not a good food for diabetes mellitus cats, but once he was eating that one, it was much easier to transition him to other wet food flavors.
ECID and others on this site probably followed a totally different protocol for doing this. Plus your cat might be less (or more) stubborn than mine. If you are going to try it the way I described here, a good clue on what kinds of flavors your cat might not try as hard to cover up would be if he/she tries to steal certain table scraps differentially (ie, fish, pork ribs, etc.). Mine wasn't into table scraps (except milk)- so we didn't have much of a starting point. But some of canned foods resemble human food, if your cat is into that. I can give some examples of these if you end up needing them.
If you free feed, step one would be to establish routine mealtimes instead. Also, this is all assuming your cat won't go anywhere near wet food to begin with. Others will have good ideas to consider also...