I just wash mine in the sink with washing up liquid to clean it then let it air dry x
You can't sterilize it because of the hole if water gets inside it will grow mold. What I do to clean it is take it to the sink and put my thumb tightly over the hole to make sure water doesn't get inside and then I wash it with baby bottle dish soap and rinse well. At the end if you squeeze it and it squeaks normally then you did a good job of not letting water in. If you have a UV (water free) sterilizer you could use that. You could also wipe it down with the munchkin pacifier wipes but because its going in babys mouth i wouldn't use wipes with any harsh chemicals.
I also agree with what @Bee said for cleaning. You can use a disinfecting wipe or spray that is safe for food contact surfaces that doesn’t need to be wiped/rinsed off first. I would spot test an area to make sure it doesn’t take off the paint on the teether first. Daycares and preschools have to disinfect mouthed items/toys everyday.
As above or wash and freeze it. Freezing it kills germs and it’s nice and cold for those teething moments x
I wipe mine with a clean hot cloth x
Agree with what @Bee said
Wipe it with a hot cloth and soap, then freeze it
I use baking soda cleaning wipes
I use a cold steriliser so just chuck it in there and any other plastic toys too!