This is going to look and feel so very wrong, but trust me it works. Hold the bread cut-side down and let the water run over the entire baguette for 10-20 seconds. You don’t want it sopping wet–just damp enough to absorb the moisture lost when the bread went stale.
Depending on how wet your bread was, it should take 5-10 minutes for the baguette to warm through. As the bread heats up, any excess water will evaporate leaving you with fluffy warm bread and a nice crisp crust.