Upon arriving home, prepare a mixture of one part vinegar and 10 parts water in a large bowl or pot. White vinegar or apple cider vinegar work best.
Dump berries into mixture and stir until all berries have been doused in mixture.
Drain, and rinse if so desire. Mixture is diluted enough that does not affect taste in my opinion, but it could be stronger to others. Place in refrigerator until time to eat!
Voila! The vinegar kills mold spores and other bacteria on the fruit, and keeps raspberries fresh for a week, and strawberries for two weeks. I haven't tried it on blueberries yet, but I imagine just as fantastic of results. Hope it works as well for you as it has for me!