First wash it with warm water. ("hot" tap water is probably fine, but not boiling). Let it cool then fill with cool water (use fresh water, don't let the warm water cool). Add a cup of bleach to the water and let the tank set at least two hours. (Add the water then the bleach).
Rinse twice then fill with water and add a double dose of water conditioner. Let sit at least half an hour. Empty and you should be good!
I only use vinegar to remove hard water deposits, which you are unlikely to have in a tank used by a non-aquatic animal. Nothing wrong with using it, but it really won't help much.