I've used this
lemon squeezer but forgot to clean it.
Now that I need it again I can't clean the mold in it (please see the picture), because it's too narrow.
Is there a practical way to clean it?
If your lemon squeezer is dishwasher safe, the spraying jets and hot water of the dishwasher may be able to kill and blast off all the mold. Just make sure to secure the lemon squeezer so it doesn't fly off the rack in the dishwasher and bang around; it might wind up in a place where water isn't spraying, and it won't get cleaned.
You could bathe the lemon squeezer in a bath of bleach & water for a little bit of time then clean the mold off using cotton buds.
If you don't like to use bleach, you could always try just with soapy water & cotton buds to clean them.
Those kettle-sized steam cleaners are pretty handy for jobs like this.