Wondering if there is anything I can do for frosting that is already made that is too sweet?

I've read that flour, cornstarch,or salt can be added to cut down on the sweetness... I would use all in small amounts until you get the flavor you desire (especially the salt because you don't want to have salty frosting lol...) I imagine that salty buttercream is way worse than buttercream that is too sweet

If the frosting is thick you can add whipped cream. The consistency will change but it will cut the sweetness.

Add a salt dissolved in a bit of hot water. It does help cut back on the sweet! I use a tsp of salt when I make my buttercream.

Start by adding as pinch of salt. Alot of recipes call for a pinch of salt to cut down on the weetness.

If I'm making American buttercream (like Indy's) then I use WAY more than a pinch. I use a small palmful of popcorn salt (probably close to a tablespoon). You can also add some juice from a lemon too. I learned that from one of Toba's books. It really does work. You don't even taste the lemon.

If your recipe has butter, then you can use SOME salted butter. I accidentally picked up salted butter a few weeks ago and the buttercream was very salty. Luckily that batch was garbage anyway (way too soft) so I tossed it.

Assuming you don't mind thinning it out a bit, I've diluted my salt in a bit of water and have added the mixture little by little being careful I don't make it too thin and making sure its not too salty.

Also, frosting will be sweet when you taste it off your finger, but it's mm mm good with cake!!!