This is the best method I’ve ever tried for keeping strawberries fresh. The batch that I did kept for a whole week. The strawberries should be left whole and NOT capped.
Whole strawberries
A solution of water and white vinegar - 3:1
Recipe
Make enough of the vinegar solution to cover the strawberries (you can dunk the strawberries in batches so that you don't have to do a huge amount of the solution).
Dunk the strawberries in the solution - just let them soak for less than a minute. Remove from the solution and rinse briefly. Dry THOROUGHLY (they suggest a salad spinner lined with paper towels). Transfer to a paper towel lined container (I used one that was large enough that I could spread them out a bit) and cover LOOSELY. Store in the refrigerator.