We had this problem badly in our bathroom. We put a frosted film over the window (for privacy) and that stopped the condensation. I don’t know how/why, but it worked. The condensation was so bad that it was causing mould, and we were having to dry the windows with a towel at least twice a day.

The film we used is removable - you just spray the window with a light mist of soapy water, put the film on, and squeegee out the air bubbles.