Soak your cakes in simple syrup before you stack them, so that it doesn't drip down the sides. Also, allow the simple syrup to soak in fully before moving forward with buttercream or decoration!
In a small saucepan, combine the sugar and water and bring to a boil over medium heat, stirring until the sugar is completely dissolved.
Once your mixture has come to a boil, whisk in 2 tbsp of instant coffee.
Let cool completely, then fill your simple syrup bottle or cover and store in the fridge for up to one month.