Does it matter if you put the syrup on layers before you freeze them, or should you wait until they thaw out?

I do it before freezing but it doesn't matter. I like to get all the messyness of assembling the cake done and get it frozen then just have to do the icing and decor. It just seems more reasonable to me but I'm sure plenty of people do it after thawing.

I just wanted to thank everyone for all the great info on this topic. I'm so glad that I found it! I tried the syrup this weekend on some chocolate mini cupcakes that I baked. They were a teeny bit dry for my taste. Instead of starting up a new batch, I made the syrup and brushed it onto each cupcake. It was a miracle! They tasted so moist - not soggy. I just made the syrup with sugar and water but now I really want to try other flavour combinations and I'll definitely be putting onto all of my cakes!

Thanks again everyone!

I've tried sugar, water and a little of Anise and the results have been a success

ok so what's the best method for getting the syrup on the cake - spray, pour (with bottle), or brush on? (Leah what do you do?)

but I tried simple syrup in the past and had a problem. I used 1 cup sugar and 2 cups water; boiled and cooled then brushed onto layers. I filled and iced the cake with buttercream dream and covered in MMF. I tasted the cake before brushing with simple syrup as well as the buttercream and neither one were really sweet. However, when the cake was cut (24 hours or so later), although it was wonderfully moist, it was REALLY sweet! The next time I tried this, I used 1/2 cup sugar to 2 cups water. Same thing happened! I would like to use this method because I loved the moisture it adds to the cake and how it holds the cake together as described here, but I cannot sell or serve an extremely sweet cakes! I know buttercream and MMF are both sweet but I must be doing something wrong because it happens after sitting with all the components together! Please help!

I have used Anis with sugar & water and it tastes pretty good.