In a large bowl combine baking soda, citric acid, cornstarch, epsom salt and pigment.
Pour in melted coconut oil and essential oil. Mix until well combined.
Lightly spray witch hazel a few times until you can gather the mix in your fist and it holds its shape. If it easily falls apart then you might need 1-3 more sprays of witch hazel. Avoid spraying too much or your mix will start fizzing. You only need enough to slightly dampen the mix.
Press the mix into your mold and allow them to set for a few hours or overnight, before removing.
Melt soap and dip the top of the donut bath bombs twice. Immediately add sprinkles. Let soap set for 10 minutes.