Baguettes are notoriously short-lived. They will often get stale by the end of the day you buy them. But although many people outside of France may not know it, the French have a tried-and-true method for reviving stale baguettes. It works best with a true, French-style baguette--the kind with a hard crust and fluffy interior.
Eat as much as possible of the baguette when it is fresh. It will never be quite this good again.
Save leftover baguette in a loosely closed bag. The ideal container is the paper bag baguettes are usually sold in, just folded over to lessen the exposure to air. Avoid storing in a tightly sealed plastic bag, because this will soften the crust.
Moisten your hands with tap water, and briefly massage the crust of the second-day baguette, which is probably too hard to cut or chew. Just barely moisten the crust.
Place the baguette in a microwave at low or medium power for 30 to 60 seconds. Alternatively, put it in a conventional oven preheated to about 149 degrees Celsius for a few minutes.
Take the baguette out of the microwave or oven. It will once again soft enough to cut or chew, while the crust remains crispy. A good-quality baguette will even give off that yeasty, oven-fresh fragrance again.
Use the baguette for a sandwich or as accompaniment to a meal, or toast as a tartine.