So I'm out of food, my brewer got a little over excited and brewed EVERYTHING. What's the quickest way to make some more food? My dwarves are hungry!
Brewing would have left seeds behind. Press 'z' to go to your fort overview and then get into the kitchen menu. Enable the cooking of whichever seeds you have most of, or that you don't have any plans to plant in your farms. Your cook will turn them into prepared meals. Then keep an eye on your seed stocks as you don't want your cook to get overexcited and cook all the seeds too.
Gathering Herbs is the easiest way. If you're in a desert / tundra, breach the caverns and herbalize from there.
If you have extra cats, you may consider slaughtering them as well.
Some people frown upon it, but you can also enable cooking of booze.
I recently noticed a cooking quirk in DF. When I tell my cook to make some lavish meals and he has both booze and solid ingredients at hand, he tends to grab and cook the solid ingredients and ignore the booze. So if I tell him to cook a lavish meal (requiring 4 items) he will four solid items and make a small number (matches the number of input ingredients) of lavish meals.
If I forbid all but one of the solid items and there are multiple barrels of booze nearby, he will produce 30-70 lavish meals from the one solid item and massive amounts of booze. So one quick way of converting booze back into food is to forbid all but one solid item and then tell your cook to make a lavish meal using that item and a bunch of nearby booze barrels.
Cooking a meal still requires one solid item, but once you have a solid item, don't let your dwarves eat it but rather use it in your kitchen to convert booze to solid meals. Those two leafs you gathered from outside plus 70 dwarven wine will convert to 72 leaf wine roasts. 72 roasts will feed your fortress for a long time.
In general, it's probably safest to forbid a few stacks of food, barrels of booze, and whatever else you want to reserve for emergencies to prevent them from being used up by your hyperactive dwarves. You can unforbid them in an emergency if you run out.