In the feature story, "Blondie: Heritage of a Super-Bumstead", Dagwood suffers from a jumpy stomach. To calm it down, he creates one of his signature sandwiches.
The ingredients, as disclosed in the story: relish, mustard, pickles, olives, catsup, horseradish, sardines, peanut butter, cheese, beans, onions, and mayonnaise.
Dagwood eats only half the sandwich. Alexander's friends disturb Dagwood's nap, and Dag erupts in fury! Dagwood demolishes a tree, notices that he's damaged the front door, and quickly realizes that his sandwich has granted him super powers! He retrieves the other half of the sandwich from the refrigerator, but before he can analyze the contents, Blondie drags him away to fix the front door!
While Dagwood repairs the front door, Daisy and her pups devour every last bit of sandwich, causing Dagwood to start from scratch. (It is not shown if the dogs develop super powers.) Will Dagwood rediscover the source of his powers?
The editors tease further adventures, and according to the Grand Comics Database, a second story was printed in the very next issue. (This is quite unusual for a licensed comicbook. Usually, the editors would wait for sales figures and reader letters before deciding to continue a particular story. Perhaps the writer and artist had this written as a two-parter, and the editors decided to split it over two issues to maximize sales.)
Blondie #214 showcases the five-page "Tonic... With A Real Kick" featuring "Super-Dagwood". Since the series ended shortly thereafter, I suspect they do not exist. (Although I know many fanboys are salivating over the idea of "Super Blondie"...) John Byrne did work at Charlton during that time, and could revive the idea. (Dagwood and Blondie make a cameo in Fantastic Four #276, when Reed and Sue move to suburban Connecticut.)
(Hey... I just noticed... those big black eyes, the strange feathered hair... Dagwood looks like an extraterrestrial alien!)