There often comes the time when saying the truth to someone becomes the hardest. Nevertheless, saying it then becomes most important.
I've had been through multiple such situations where I ran hundreds of simulations in my mind to find a way to get out of the situation without telling the truth.
I couldn't find a single way to do that.
I had to tell the truth and face that person. There were no other choices. Also, it was the noblest thing to do at that moment.
Making up some excuse to cover up the truth is not only shameful but also terribly wrong. Doing that you're stealing someone's right to know the truth.
Should you find yourself in that situation, go the obvious way - tell the truth.
It'll be hard but it'll be totally worth it.