I have a couple of containers of icing from previous cakes, that I will be using tonite. Can you think of something I can add to cut the sweetness a little? Seems the longer they sat (in the fridge) the sweeter they got!

a pinch or two of salt usually work for me to cut the sweetness.

Lemon juice might work.

I tried lemon juice once and loved the outcome. If it waters it down too much, just add some cornstarch. GL

Be careful with the lemon juice because it will effect your icing colors. I usually throw in a dash of salt and it cuts the sickening sweet taste.