The three main versions of this saying that a Google search finds are "There's a pork chop in every beer," "There's a sandwich in every beer," and "There's a steak in every beer." None of them appear to be very old sayings. Here's the rundown on each one.
'a pork chop in every beer'
A posting from September 23, 2000, at StraightDope.com titled "The New and Improved Signature Thread," which collects "favorite signatures on the board," lists this as one of them:
There's a pork chop in every beer.
An October 2, 2002, question at the message board of the same site asks whether a (12-ounce, presumably) beer has the same nutritional value as a pork chop, a question that suggests why someone thought of equating beer and pork chops in the first place. (One answer to the Straight Dope query made the seemingly sensible observation that, although the total calories from the two items might be roughly equal, the pork chop's calories come from protein and fat, while the beer's come from carbohydrates and alcohol.)
The 2000 match is the earliest one that my Google search could find.
'a sandwich in every beer'
The earliest Google match for this phrase is an October 9, 2003, comment on Fark.com, which says simply "There's a sandwich in every beer."
However, a Google Books search finds an instance from Robert Seidenberg, "Menace to Propriety," in Ski magazine (December 1995):
4:10 Last run of the day. "In every beer there's a sandwich," philosophizes Crane. "And I'm hungry. It's time for the 'Menace to Sobriety' part of the equation."
'a steak in every beer'
This expression, which appears to be especially common in Australia, has an earliest Google search occurrence of February 17, 2002, at the Bodybuilding.com forums, where a poster says this:
No way. They say there's a steak in every beer. More beer i say
It seems highly likely that one of these three expressions supplied the inspiration for the other two, but the earliest recorded instances I've been able to find for each variant are fairly closely bunched: "sandwich," December 1995; "pork chop," September 2000: and "steak," February 2002. I suppose that "There's a sandwich in every beer" is the current top contender, but a periodicals archive for the 1970s through the 1990s might contain older instances of every one of these expressions.
Update (May 17, 2019): 'barley sandwich' and 'liquid lunch'
I had never come across the expression "barley sandwich" (which Phil Sweet cites in a comment below this answer), but a bit of research indicates that it is older than the other expressions and may have inspired them.
The earliest match I could find in a Google Books search is from an unidentified item in Canada Poultryman, volume 60 (1973) [snippet view]:
Other items in the promotional bag worth mentioning are useful handouts such as pencils, ball point pens, notepads, and bottle openers (which are particularly useful with a barley sandwich).
The next-earliest match is from an unidentified poem in Aspen Anthology (1976) [combined snippets]:
Ancestral airs don't fill an empty glass. / I never drink before noon— / the smell spawns morning ghosts, / their dull moans mute the air. / Band an elbow with me, John Calvin, / God gave that grain for a barley sandwich / and good whiskey hymns / ...
And from Guy Vanderhaeghe, "Cages," in Prism International (Autumn 1981), a periodical published by the Department of Creative Writing at the University of British Columbia:
That reminded him. He jumped out of the chair and gawked up and down the deserted street. "It's almost one o'clock. On a school night. I'll kick his ass." He sat down and watched the screen for a while and sucked on his barley sandwich.
A later item in Michigan Beer Guide, volume 10 (2006) makes the wholesome meal argument explicit:
Are you aware that there may be health benefits to that bottle of beer? (CanWest News Service). Health benefits ranging from proteins and antioxidants to B vitamins; the "barley sandwich" contains a surprising collection of substances good for you. Since the beginning of civilization beer has been used both as a source of water and of food. Beer contains malt from barley or wheat, a source of sugars, carbohydrates, proteins, amino acids and antioxidants. Hops are full of antibacterial and anti-carcinogenic compounds, and bitters that stimulate the appetite. Yeast provides alcohol, carbon dioxide and vitamin B complex. Then water, which could contain calcium sulphate, magnesium sulphate, sodium and potassium chloride, zinc, iron, silica and other trace minerals.
The expression "barley sandwich" in turn may owe something to "liquid lunch," which originated as a non-alcoholic protein-rich concoction in the early 1900s but eventually became a slang term for an alcohol-instead-of-food "lunch."
The alcohol-free expression appears, for example, in E.F. White, "The Fountain and Its Accessories," in The Spatula (July 1903):
Our Liquid Lunch.
Last winter as the sales commenced to lessen and idle hours to increase I commenced to advertise my "liquid lunch" both "hot" and "cold." The means used to advertise this specialty, was small 1 inch advertisements in the daily paper. These were worded in various ways calculated to attract attention to my new special the "liquid lunch" and it was a success. It took the people and the people took it. The beverage I used as a "liquid lunch" was an egg Malted Milk Coffee, a formula for which appeared not long since in THE SPATULA so that I will not repeat it here.
But soon enough the serious drinkers lay claim to the expression. From Walter Atkinson, "Between Drinks," in The Phi Gamma Delta (March 1912):
Said the Highball to the Toddy: / "Man is fickle. Ah! 'tis true, / He adores me for a time, and / Then abruptly turns to you. / For example, there's the Fiji— / When convention times comes 'round, / To the good old Liquid Lunch Club / Loud my praises will he sound.
But for my poor Liquid Lunch Club, / 'Tis with pity in my breast, / That I say: why let them die of thirst / When they might have the best.
The term "Fiji" in this quotation refers to a member of the Phi Gamma Delta fraternity.
And from George Kaufman & Edna Ferber, Dinner at Eight: A Play in Three Acts (1932):
LARRY. What's happened to you? Why all the animal spirits?
PAULA. Oh, nothing. Just girlish vivacity. And hunger.
PAULA. Would you give a girl a cup of coffee? Nothing else.
LARRY. Of course. (Reaches for the phone) What's the matter? Didn't you have any lunch?
PAULA. Well—I had a sort of liquid lunch.
LARRY. (In phone) Buttered. That's all. Right away, please. (Hangs up; sits R. of her) Now, what's got into you?
PAULA. I had lunch in a speakeasy. I had lunch in a speakeasy with Ernest. I had three double Martini cocktails and Ernest had double lamb chop with spinach a dollar fifty.
Paula's "liquid lunch" is, of course, the quintessential three-martini lunch (aka the "businessman's lunch"). It's certainly a far cry from the homely "barley sandwich." Nevertheless, the notion of alcoholic beverages as ersatz food does link the two terms—although I doubt that anyone has ever made the nutritional claim "a third of a pork chop in every martini—with a twist!"