Melt the butter in a large pot over medium heat. Then add the vegan marshmallows and stir until they have melted.
Vegan marshmallows don't melt like traditional marshmallows. You will find they melt into a large, for lack of a better word, blob. This is okay!
Remove the pot from the element and stir in the vanilla extract. Do this while the marshmallows are still warm.
Add the brown rice cereal to the pot. Again, you will want to fold the cereal into the melted marshmallows.
Mix the sprinkles into the rice krispies
Line a 9 x 13 inch pan with parchment paper and press the vegan rice krispie treat mixture into the pan.