Johnson's Brew was a tropical fruit drink. It was typically prepared by heating it in a big stock pot over a stove; later in my scouting career we started preparing it cold as well, by adding ice instead.
You'd start with a base of apple juice; typically, you want apple juice to be your largest quantity, about 2 parts apple juice to one part other juice. The reason for this is that the apple juice is pretty weak flavored: other things that you add in later are much stronger and can overpower if you overdo them.
You'd start by cutting up a couple limes and a couple lemons into slices, and tossing them in. You'd add in after that a couple oranges (sliced, again): All of these are with the peels.
You'd mix in some tropical juice: Guava, pineapple, etc. At this point, you're going to start mixing to taste: that means that you pour stuff in, stir it up, and taste it, and see if it's still overpoweringly apple flavored or not.
Other juices that can be used include pineapple, mango, peach, and other similar flavors. As you go on, you can add more fruit chunks as well: canned peaches and pears do well, and pineapple can do okay too. You're best to pour the entire can in, with the juicey sauce 'intact'; it adds to the flavor.
Serving is just dipping a ladle in, and scooping it out: You end up with a cup full of juice, with a couple of fruit bits in it. Typically, it's best eaten in the dark around a campfire: It allows you to play the "is this an orange or a lemon" game, or demonstrate your stuff by showing that you can eat a lime directly.
It's an extremely nice close to a day on a chilly evening, though I have no idea how it scales to non-40 people sized crowds. I also don't really remember if I'm remember if I'm missing something important, but I'm going to see if I can talk to people who might remember and find out.
The name of the drink is after our troop's founder, Mr. Johnson, who created the brew originally.