I'm thinking of cleaning my shoes with my sister's toothbrush
Why do you want to clean your shoes with your sister's toothbrush?
I think her toothbrush would work well to clean the shoes ands he just left it lying around unattended.
You must be annoyed that your sister left her toothbrush lying around, but you should never use it to clean your shoes. That would be very disgusting and you could cause her to get sick.
I'll rinse it off afterwards, I'm sure it will be fine.
A toothbrush should not be used to clean shoes and using it would be terribly disrespectful to your sister. Think about how she would feel and try to find a different brush to clean your shoes.