Kristen Lauletta, 32, Jessica Heyse 19, and Ashley Helfenbein, 25, were each charged with two counts of child endangerment and two counts of battery.
Police were called to the Kiddie Junction daycare centre, in Chicago, after a manager said they believed a teaching had been giving lollies to two-year-olds laced with melatonin without parental consent.
Officers found a container which originally held 120 gummy bears, but there was only 4 left.
'Allegedly, this was done in an effort to calm them down before nap time,' Des Plaines Police said in a statement.
'This is just a horrible case of bad judgement,' Police Chief William Kushner said.
But the three women maintained they weren't doing anything wrong because melatonin is an over-the-counter medication.
The teachers are scheduled to appear in court on April 4. Meanwhile police said the management of Kiddie Junction are assisting with their investigations.