Hey i'm fairly new to fondant and just the other day i had a cake to make for a birthday but the problem was,i always used MM fondant but here in India its highly difficult to purchase white marshmallows and the cake had to be white so i went on to make Michele Foster's fondant, which i must conclude was good to work with but after covering the cake with ganache and putting the fondant on it,there were air bubbles that formed and the fondant started to slide off the cake, and i didn't chill the cake after putting the ganache because i was scared that the fondant would start to sweat if i put it on the cold cake because our temperature here is too high and to add to it,its very humid..and later this month i have a two tiered cake to make,n its only going to get hotter here,so how can i prevent this fro happening again?
If it was hot enough, your ganache never set, so you essentially put a fondant covering over a soft chocolate (a flavorful oily fat) base. It had no choice but to slide.
I'll be honest, I've been in India in the month of May and I have no idea how you would go about making a cake to withstand that type of heat & humidity without air conditioning and refrigeration up to the moment of display.
I would think that you would have to refrigerate once covering with ganache, put the fondant on the cake while it's at least very cool, and then refrigerate again.
You can minimize sweating by boxing the cake & wrapping the box with some aluminum foil and/or saran wrap. Let the cake come to room temp while the box is fully wrapped and only then remove it from the box.
Even doing that, if the temp is above 90F, the cake will suffer the longer it's out of refrigeration.
You might get a better result with an American Buttercream (powdered sugar, high ratio shortening, heavy cream type recipe), but I really doubt that high ration vegetable shortening is readily available in India.
You could try making a stiffer ganache using more chocolate, darker chocolate, and less heavy cream.