Use them to start to build some standard policies for your company - there are also some certifications that are very light weight and will get you into a shape where you have answers to most of the questions already (e.g. in the UK you can do Cyber Essentials).

Build up a database of the questions and your answers so that you already have most of the answers close at hand.

Unfortunately it's a cost of doing business and as someone else pointed out. If you've reached the stage where IT is sending you questionnaires you are probably very close to closing the deal.

The size of the deal should make filling these things in just an inconvenience.