How Can I crispen soggy donuts?

Preheat the oven to 350 degrees and lay doughnuts directly on the upper rack. Heat for 10 minutes, turn off oven and open door. Leave doughtnuts on rack until oven is cool to touch, then remove. Yummy.

toast them in the oven for 10 min at 300 degrees

It is important not to have them on a solid thing- like a cookie sheet. Rubberguy is right on target.  If you have a perforated microwave  plate, you could give this a tryal and error.  I have never done this, but  I use the microwave to freshen bread and cake.  (about 10 sec  on high with 1100 watts works for me.)

There are two important questions to ask before engaging in this activity

    1. What kind of donuts are they?  Filled ones can be problematic. 

    2. Why are they soggy? 

Please recall that there are no calories in the holes!

 JayR