I got a request for fresh fruit as a filling (strawberries or peaches or both).
The cake is a 2 tier fondant cake. I won't be refridgerating this cake.

I'm worried that the cake layers will slide bc of the fresh fruit between or even make the cake mushy/too moist. I'm also worried for freshness since i'll be filling it 2 days before delivery. (delivery on sat. Filling on thursday)

This person also requested a custard filling. She may want the fresh fruit and custard combined together in one layer of filling. I've done this before with a buttercream cake and the layers slid around when we were serving the cake. And that buttercream cake didnt have a 2nd tier on top of it.

HELP! WHat should I do? Do I have to tell this client that I cant do fresh fruit? and how do I explain that I cant do fresh fruit?

I did this for my brothers wedding cake in June. I made a vanilla mousse using two cups heavy whipping cream and one small box instant vanilla pudding. Whip until peaks form. Then I rinsed and sliced the strawberries and laid them out on paper towels. I also covered them with paper towels to help remove some of the juices. I put a layer of mousse and then a nice layer of strawberries. I didn't have any problems with the filling bleeding or sliding. I would recommend filling and decorating only one day before the event. Strawberries tend to turn mushy. Keep refrigerated until party. Our cake sat out for four hours and was fine. Try the mousse I bet you will fall in love with it I did. Extremely stable and I get so many compliments. Also works well with chocolate fudge and banana pudding. I have used banana slices on top of the banana mousse yum.

Thanks sweettreat101 your recipe sounds yummy. but i cant refrigerate the cake. its a fondant cake. I dont want to put fondant in the refrigerator bc im concerned with the sweating and the colors bleeding.

If anyone else has anymore advice that'd be great!

I don't know where you live but I never have problems with my cakes sweating and I put every cake in the fridge. You could use Better creme and instant pudding for a filling then you wouldn't have to refrigerate.