You have to be patient, but it is possible.
The way that a Keurig coffee maker works is as follows.
1) the machine pokes a hole in the top of the K-cup for the water to come in
2) the machine pokes a hole in the bottom of the K-cup for the brewed coffee to come out.
3) when you start brewing the Keurig pumps water (fairly high pressure) through the top hole.
4) the coffee brews and the incoming water pushes the brewed coffee out the bottom.
5) this continues until the brewing amount is done.
6) the Keurig then pumps some air (not compressed, just regular) into the K-cup to push out all the water
7) All done
It would be easy enough for you to poke holes in the top and bottom. The trick is for you to get boiling water going through at just the right speed to brew but not overbrew and not overflow. That’s the hard part.
Or you could open the k-cups you stole and dump the coffee in a regular Mr Coffee filter and pour boiling water over it to brew.
Both of these are workable alternatives.
Why are you a thief?