This. I was lucky enough to get Cleveland stadium mustard as a birthday gift and have had many hotdogs in the past month, but it’s just not the same 
My mother was very fond of, and very good at, ice skating. Some of my earliest memories are of her taking my siblings and me early in the mornings to the local skating rink, teaching us how to do figure eights and such.
There was a little kiosk at the rink that served mostly hot chocolate and scones. The hot chocolate was homemade and rich. The scones were actually deep fried bread served with powdered sugar sifted over, like they were too lazy to make proper doughnuts or something. The scent of the frying dough would hit you as soon as you walked in the door of the rink.
The skating was wonderful fun, but oh, my – hot chocolate and scones after will never taste better than they did then and there.
I have other such memories, but this the first to spring to mind. 
I’m sure their locations affected how good the two best fish & chips I’ve had.
First was ono at an open air, beachside restaurant on Ka’anapali Beach on Maui on the last day of my honeymoon. Second was in Dingle, Ireland halfway through an amazing drive of the peninsula, eaten at a seaside park bench and served at the window by an American expat wearing a Raiders cap.
Oh, another festival one: Bozeman, MT has a Sweet Pea Arts Festival every summer, about $10 (well, probably $15 now) for a full weekend of five stages of entertainment, plus a craft show. And of course festival food, most of which was fundraisers for various local nonprofits. Including the Tater Pig: A potato with a hole cored through it, filled with a sausage, baked, and then topped with all the usual baked-potato works. I suppose I could make it at home… but Sweet Pea just wouldn’t have been the same without it.
The best rehearsal dinner I ever went to was for my childhood friend’s wedding. It was a gigantic lobster bake over a bonfire in the groom’s parents’ backyard in Maine in the summertime. I remember being blissfully covered in shellfish juice and garlic butter.
Fresh chocolate chip croissants at NYC’s Zabar’s, still hot out of the oven. Actually, any food bought at Zabar’s.
Buying and eating crêpes on the sidewalks of Paris.
I don’t know if it was the location that made it special or the location. I was driving to Eureka and stopped in Hopland for breakfast at the little cafe in town (Bluebird?). I ordered an Ortega chili and Swiss cheese omelet. Nothing special. Something I’ve eaten dozens of times. But it was absolutely delicious! Like I noticed how good it tasted. I figured out that it must have been that the eggs were super fresh, because Hopland is so close to Santa Rosa (the egg capital of the world!).
I can still remember how yummy the fish and chips at the hole-in-the-wall place near Geary and Larkin we got after watching an old Jack Lemmon movie (April Fools? something like that) in the summer of 1969. A friend of the people I was staying with that summer was in the Navy and shipping out to Vietnam the next day. It was his favorite movie, so that’s why we watched it. A little weird for a rom-com like that being his fav, but I think it was a warm memory for him to take with him. Next morning we walked out to middle of the Golden Gate Bridge to wave at him as his shipped passed below. Then, we had hot chocolate at the Roundhouse. Never had fish and chips nor hot chocolate* so good again.
*Only kinda exception was the hot chocolate at The Apple Pan when the Mad Whipped Cream Man worked there.
Boardwalk fries on the boardwalk.
Thirded. Farmer John sells Dodger Dogs retail, but they never taste as good as the ones grilled under the center field bleachers at Chavez Ravine.
Bologna and American cheese on white bread. I’d never touch it at home, but perfect when we’re camping.
I always say the best wine I ever had was the first day I was in Venice.
The hotel we were staying in had an outdoor bar right on the Grand Canal. Sitting in the evening sun, watching Venice go by (a place I had wanted to go for years) - to be honest, they could have given me the red cordial instead of wine and I would have loved it.
Hitchhiking east out of Tucson, I got a long ride in the back of a pickup with a couple other lucky but cold folks. The driver pulled into a rest area around Pyote, Texas at dusk and roasted liver over charcoals. It tasted damn good.
Both mentioned in some form:
- Thrasher’s french fries on the boardwalk
- Hot dog at any/every baseball game
By the sea, by the sea, by the beautiful sea… (as seen upthread)
Oysters, sold and served by old women at the water’s edge along with local white wine.
That’s like pizza in Amalfi, Italy. Buy a little handmade beauty at the kiosk just inside the city wall, then sit out on the pier and watch the Mediterranean.
Similar: Stroll the old rail grade up Mt Tamalpais, north of San Francisco. Stop in the cottage halfway for fresh lemonade and maybe a munch. Sit on the open porch overlooking EVERYTHING! Ocean; bay; bridges; cities; mountains - all lie before you.
A different goodie: Wander through Washington Square in Manhattan munching a giant hot pretzel dipped in spicy mustard while observing chess players and mimes. They’re still there, right?
Or enjoy California history on the Kit Carson Pass Highway at Kirkwood Inn, bisected by the Amador-Alpine county line. During Prohibition, the Inn’s bar was on wheels. When deputies from one county came to raid the place, the bar was rolled over into the other county. Drinks are still served across the line.
Sipping a thermos of tea after easily climbing volcanic Mt Lassen is also memorable.
We had the former just yesterday.
Drinking black coffee in a paper cup from a vending machine, walking through a park on a freezing day. That vending machine coffee was awful, might not even have been coffee, but it tasted great in cold weather.
In middle and high school, I used to ride my bike everywhere. Headed to or from home, I’d get a Dr. Pepper from a soda machine at a gas station. The machine was too cold, but for some reason only the Dr. Pepper would achieve a near ICEE state. Drenched in sweat, I’d get a Dr. Pepper or two and guzzle it next to the machine. I’d sometimes get an extra and put it my backpack for later, but since I hate Dr. Pepper (though not as much as root beer which I’ll never drink) it never was the same.
I love to get a pint of real ice cream and eat it outside on very cold days. It just tastes better that way.
I did a 5-week volunteer trip to Costa Rica in my 20s. I ate a lot of fresh tropical fruits, white rice and black beans, and salad. There was always a bottle of Lizano sauce on the table, and I got in the habit of putting it on just about everything. It was kind of like a cross between salad dressing and steak sauce. I bought a bottle to take home, but it just wasn’t the same.