The first jingles I remember are from 1945, when I was six years old:I’m the Minute Rice Man, with a new kind if rice:

Minute Rice, Minute Rice, Minute Rice
New Minute Rice is so quick, my oh my
Fluffy tender rice in the twinkle of an eye
For a new and better rice, just follow my advice
Minute Rice, Minute Rice, Minute Rice

Eight reps of the product name! Very old school. Strangely, the second jingle I remember was also for Minute Rice. Even at the time I thought that was a little odd that there were two different ones on at the same time. This one had a melody I could tell was supposed to be Chinese-y, and was sung by a man in a Chinese accent:

Here’s some news for hungry family, very fine advice (gong sound)
Cook for hungry family, quick new Minute Rice (gong)
(I can’t remember this next line. It has been 78 years. I couldn’t find it online. But it went…)
da da da da dadada da da dadada (gong)
Cook for hungry family, quick new Minute Rice (gong)

The next jingle I remember was for Instant Ralston on the Tom Mix Ralston Straight Shooters radio show. It was to the tune of “When the Bloom is on the Sage”, a popular cowboy song from 1930, written by Fred Howard Wright and Nat Vincent, aka The Happy Chappies. The opening lines: “When it’s roundup time in Texas/And the bloom is on the sage/Then I long to be in Texas/Back a-riding on the range”. Until the fifth grade, I was addicted to three five-days-a-week, after-school, 15-minute radio serials––Superman (sponsored by Kellogg’s Pep, which turned to slimy mush as soon as you added milk, but had great premiums inside the box), Captain Midnight and his Secret Squadron (from Ovaltine, which previously sponsored Little Orphan Annie, and would go on the sponsor Howdy Doody), and then Tom Mix (courtesy of Instant Ralston, and Shredded Ralston, which would later be re-named Wheat Chex). I loved Shredded Ralston. “They’re out of this world!”, said the announcer. “He’s right!” I said, upon first tasting them. “They ARE out of this world!” Mom laughed. Captain Midnight had my all-time favorite villains––Ivan Shark, and his daughter, Fury. Their henchman was an Asian named Fang.
Consensus seems to be that the first jingle was for Wheaties. It was sung by a male quartet and delivered acapella:

Have you tried Wheaties (hummmmmmm)
Wheaties are delicious
Lots of energy
Wheaties
Wheaties, the breakfast of cham-pions!

I loved the way they hit the P in champions.
I read in one place that that first radio jingle dated to 1926, another place put it in 1927, yet another in 1929. In the early days of radio, many people felt it was so miraculous a medium that using it for advertising was almost profane. Talk about innocent times. Of course, the “needs” of the market prevailed, but the percentage of air time that could be used for advertising was strictly limited, until it was expanded by Ronald Reagan, who explained in his kind fatherly way that allowing advertisers more time to pump out their weasel words was “getting the government off our backs”. His crackpot premise was that all government regulations were bad, nay, evil. In any event, it was decided in the 1920s that advertising in song form was exempt from advertising time restrictions, thus giving birth to a new art form, the jingle, or, as it was first called, the singing commercial. I, for one, rejoice. I truly wish an effort was made to collect every jingle ever made, especially the frequently deeply strange local ones. I lament the likely permanent loss of a spoken word jingle, out of mid-50s Milwaukee, for the Charles Lubotsky Tire Company. At the time, I liked to believe that it was delivered by Charles Lubotsky himself, but that’s unlikely. The voice started by saying, “We have a wide selection,” and then went into a hard-driving high energy delivery. My personal high point was when the voice said, “so come in NOW”, snarling out NOW in a way that made the hair on the back of my head stand up. Early White rap at its finest. Perhaps the earliest White rap was delivered in The Music Man by Professor Howard Hill in his epic “Trouble in River City”. Wait, That’s not right. Charles Lubotsky came first.
It’s possible two other real contenders for the earliest jingle are the 1903 waltz “Under the Anheuser Bush”, or 1905’s “In My Merry Oldsmobile”, but those weren’t made for commercial radio. They were commissioned to mimic the style of then-popular songs, an old trick today, like what Coca-Cola did in 1971 with “Buy the World a Coke”, a tune influenced by the likes of Burt Bacharach, Ray Stevens and the Broadway show Hair. That Coke jingle later went on to find the pop charts on its own, as “I’d Like to Teach the World to Sing”. Life imitating art. Brands copying popular songs. People buying the same thing, over and over.
Complicating matters in finding the true first, I read somewhere that silent movies sometimes featured people––perhaps accompanying the pianist––singing the earliest form of a promotional jingle. I don’t know where I got that from, and have not been able to find any confirming references online. The search for the beginning continues. The music for 1939’s “Pepsi-Cola Hits the Spot” can be traced back to an English hunting song from 1824, which is itself a variation on a tune that can traced back to 1695 London, proving that no good song ever goes forgotten for very long or, conversely, in the positive, that every good song will keep finding a place to be heard.
I’ve heard of pre-radio jingles, but the only ones I’ve been able to put my hands on were recorded on 78-RPM records in 1926 or 7 by the NuGrape Twins: “I Got Your Ice-Cold NuGrape” and “Nugrape—A Flavor You Can’t Forget”. The former is a better song. The second line of that song may be the strangest ever found in a jingle:

I got a NuGrape, nice and fine
The rings around the bottle is a ginger wine
I got your ice cold NuGrape
I got a NuGrape, nice and fine
Got plenty imitations, but there’s none like mine
I got your ice cold NuGrape
Way down yonder in the Promised Land
A-run and tell your mama, “Here the NuGrape man”
I got your ice cold NuGrape
Little children in the backyard, playin’ in the sand
A-run and tell your mama, “Here the NuGrape man”
I got your ice cold NuGrape
Whеn you feeling kind of blue
A-do not know what ailin’ you
Get a NuGrape from thе store
Then you’ll have the blues no more
I got your ice cold NuGrape
What’s that makes your lips go plippity-plopp?
When you drink a NuGrape, you don’t know when to stop
I got your ice cold NuGrape
If from work you come home late
Rolling pin waits at the gate
Smile and ‘prise her with NuGrape
Then you’ll sneak through in good shape
I got your ice cold NuGrape
Sister Mary has a beau
Says he’s crazy and loves her so
Buys a NuGrape every day
Know he’s bound to win that way
I got your ice cold NuGrape

The rolling pin reference in verse seven (wow, an eight-verse jingle) may be obscure to younger readers. The angry wife chasing her husband while armed with a rolling pin used to be a common image, usually found in newspaper comic strips. You could say it was an early 20th-century meme.   You can hear “I Got Your Ice-Cold NuGrape” on YouTube. It’s well worth your while. Just two voices and a somewhat raggedy piano. If these two jingles exist, there must be more. I’m going to look for a jingle expert. Anybody know who’s on the top of this field? Yoo-hoo!