I guess I’m too subtle.
I was 30-something, married with kids, when we took my visiting mother out to dinner. We had been waiting for a long time, as the place was crowded, and my mother complained of being thirsty. I had a full glass of water and offered it to her. Her reply was “You know I NEVER drink water!” I had no idea. I said “Why don’t you drink water?” She says “You don’t know what they put in it!” 
Sorry, totally overlooked your post.
What?
For myself: Tofu. How something so devoid of flavor can stink to high heaven when baked, I’ll never understand. Yeccch! 
Cooked celery. Not only do I hate the waterlogged way it tastes, I get a weird numbing sensation on my lips and tongue from it.
Anything overly spicy. Why should food hurt?
Other than that, I enjoy eating all foods.
To go along with the “water” ingredient, I once dated a girl who sent back a drink because the ice cube wasn’t right… it was stale. I’ve talked to one other person who says that’s a real thing, but… in a hard alcohol mixed drink can you really detect the minute taste qualities of a few milliliters of melted ice-water that sat in the freezer a day too long?
As a kid I used to hate and started barfing when I had to eat onions… raw or cooked in any recipe or form. Even today I make a point to specify “NO ONIONS” on any burger I order, and I open up every layer and pick through to make sure. Probably about 1/3 of the time they put them on anyway.
The really weird thing is that as an adult I’ve become somewhat adventurous in cooking, and actually like onions of different types (leeks, chives, green, yellow, purple, shallots) in all kinds of forms from raw to just-softened to caramelized to powdered. I often like to turn up the onion flavor in recipes.
But I have to control the onion prep and cooking. If I can see the starting product, control the cutting/cooking/serving, no problem. If you follow that exact same recipe step-by-step and serve it to me I’ll either spend 15 minutes plucking the pieces of onion out with tweezers and re-heating, or I just won’t be hungry that night.
My kids have grown out of it, but at one time detectable table salt or the sight of even 3-4 grains of black pepper on a plateful of mashed potatoes was enough to make them start to cry and say “Too spicey!!!” 
Yes, we (I mean they) are of an ancestry where the powerful flavors of plain boiled oatmeal can be off-putting.
It’s fishy!
My brother’s ex-wife once objected to my sister putting regular black pepper in the gravy while preparing it. My mom went along with it, but my sister was peeved. So she got some white pepper and put it in. Ex-sil never knew, ate it without a whimper.
Many things I despise have been mentioned, raisins, olives, celery, but this also applies to me. I never drink water, only in emergencies when there’s nothing else to drink present. Water is for washing. Why drink water if there are such wonderful things like soda, ice tea, coffee, tea, beer and wine?
My daughter calls raisins “the devil’s chocolate chips”. We vote with your wife.
I’m just the opposite, I like raw apples, but they give me the runs, so I avoid them.
If it was stale enough i would. Stale ice is nasty.
This is my wife’s stepfather. He’s now in his 80s, and dealing with a number of health issues, which are exacerbated by the fact that he’s continually dehydrated. His doctor has told him, repeatedly, “you need to drink more water!”, but he refuses.
If you watch him trying to drink a glass of water, he chokes on it like he’s drinking something horridly unpleasant. And, no, he doesn’t have swallowing issues or anything like that – he can drink soda or beer just fine.
My tenant simply can not drink tap water, not even filtered [I have one of those big britta bins that holds around a gallon] - will only drink some brand of bottled water, or soda. She also claims to be allergic to every form of non-nutritive sweetener. I hate telling her that there is NO filter on the ice maker in our fridge, so when she ices her bottled water, it melts down into about half tap water …
I was having issues just before I got diagnosed with the colorectal cancer where the damned thing had constricted my output to effectively a finger in diameter [15 cm anus inward was fill circumference and all the layers but not into the lymph glands, I got *extremely extremely lucky they found it with they did] which basically made my digestive tract shut down, since it couldn’t go down, food came back up instead. I ended up with nausea based on the smells of food cooking [if I had to spend a couple hours smelling something cooking, the idea of even eating the damned stuff made me nauseated - but of you could get me something off the BRAT diet with no smell of cooking there was a 50/50 chance I could choke it down] After, when on chemo I developed an amazing instant vomit reaction to the smell of an italian - italian sausage, peppers and onions frying up to make a sandwich. Even not on chemo, instead of instant vomit, it just makes me really queasy. I am still sort of smell sensitive, so we keep the pouches of precooked brown rice on hand in case something ends up to ‘smelly’ for me to eat. Otherwise, I try to eat pretty much anything I am not actively allergic to.
They make a ‘snack’ that is very much designed to get water into geriatrics - Jelly Drops.
That’s not a bad idea at all, though it looks like those aren’t yet available in the U.S.
They look like jello shots to me =)
Would jello work? I love jello - and have the odd feeling that is why jello is pretty much whenever you want it in hospitals. I know the nursing staff kept a whole fridge full of jello and yogurt and would hand them out for the asking.
I keep a 10 oz shaker jar of dehydrated lemon juice [so much more convenient than the individual packets] and a bottle of liquid splenda next to me, and a gallon of water and make lemon water [effectively 24 oz water, about a teaspoon-equivalent of lemon juice and 5 or 6 drops of splenda. Not as strong as regular lemonade, but not plain water either. I also like cranberry water - 24 oz water, about an ounce of 100 percent cranberry juice no sugar, splenda to taste, half as sweet in taste to my senses as normal cranberry juice/drink.