First, I must advise you to seek the advice of your doctor on what is needed to properly sterilize any surface. I am not a doctor and can only advise you on what type of techniques will not damage the structural integrity of your toys. Certain viruses need pressure along with heat to destroy them. As a rule I do not share butt toys so my sterilization experience is only for cleanliness.
The silicone I use can safely withstand heat up to 350 °F. In fact, I have placed them in the oven to sterilize them before. Place them upright on a glass baking dish or line any pan with aluminum foil and bake. Don’t worry about them going limp, they will still be the same firmness going out as they were going in, one reason silicone is so widely used in industrial applications today.
Boiling is also an option as water will not harm the material. Recommendations for boiling would be to stand them upright on a grate in a tall pot. Because silicone is such a good insulator they should be off the bottom as heat can build up and damage your pan or the toy. They should have water freely flowing around them at all times as well. It follows as well that they are completely dishwasher safe, top or bottom rack. Just keep them upright so they don’t pickup any impressions from the racks.
