Instead of pouring that flat brew down the drain, you might want to try a couple of these tricks.
Plant food. Beer has yeast in it and yeast is good for plants. A few tablespoons of flat brew added to the garden will enrich the soil.
Bee killer. Get yourself an old jar, punch a few 3/8" holes in its lid and then fill the jar with beer. Screw the top back on the jar and set it out in your yard where bees and wasps are a problem. The bees will love the beer, slip through the holes to have at it, and then get stuck inside the jar.
Slug and earwig killer. Bury a tuna can just up to its lip in the garden. Fill the can with beer. During the night the pests will come out to party, fall in the beer and get caught. Make sure you check the trap daily, emptying it and refilling it with new beer.
Pest distraction. Instead of the bugs bugging you at your next outdoor party, let them have beer. Simply put beer in a few containers and place them around the perimeter of the party area. The insects will flock to the beer and not to you and your guests.
Meat tenderizer. Pour a can of brew over the meat and let it marinate for at least an hour or, even better, overnight in the fridge.
Gold polish. Pour beer–not dark ale–onto a soft cloth and rub down your solid gold, gemstone- free jewelry. Use a second cloth to dry it.
Hair therapy. Mix 3 tablespoons of flat beer with ½ cup of warm water. Shampoo as usual, rub beer solution into your hair. Let set for a few minutes and then rinse. Style as usual.
Wood furniture cleaner. Poor a little flat beer onto a soft cloth an polish your furniture. Use a second clean cloth to dry.
Coffee and tea stain remover. Coffee and tea spills on the carpet can be lifted with beer. Pour a little brew on top of the stain and then rub lightly. The stain should disappear. Repeat if necessary.