What's the best treatment to get rid of double vision?

Depends: Recent onset doubling of vision can be due to trauma, nerve dysfunction or muscular disorders. The most common of these is damage to the nerves from the brain controlling eye position. You should seek an ophthalmologist or better a neuro-ophthalmologist to sort this out. You may need eye muscle surgery. Prisms and temporary patching for some forms of visual doubling.

Careful evaluation: Double vision has many causes. If it as a result of misalignment of the eyes, then examination by an ophthalmologist or neurologist is appropriate. Careful investigation is required. Once the cause has been found, and if the diplopia persists, prisms can be incorporated into glasses to correct the double vision. Occasionally sugery is required to reposition the eyeballs.