I keep a small stool on top of the garbage cans. When the dogs knock them over, the racket generally scares them away from the can. You could try something even louder like a can with coins in it.

I have a Scat Mat on the cupboards. It's a grey mat that gives off a static electric shock when touched. I bought it to keep one of the cats off the counter--Onyx used to think that was a good place to pee!! But it had the added bonus of keeping the dogs from counter surfing too. The shock is mild--doesn't hurt, just suprises them. And yes, I tested it to make sure it wouldn't hurt them!

Or you could resort to keeping the garbage cans locked up. I have kept them in the bathtub, the sink or behind closed doors.

We also don't have a microwave. We have a "food safe" that can be used for cooking when it isn't hiding food from the siberians!