Yankee Candle Calm Night Sleep Diffuser Refill Sleep good and feel good with Yankee Candle sleep diffuser refills. Blended with essential oils, the Calm Night diffuser refill is a blend of relaxing lavender and eucalyptus scents, sweetened with a touch of vanilla, known for their calming properties. Simply insert the refill directly into the diffuser – there is no need to add water and enjoy 30 nights of soothing fragrance. Yankee Candle sleep diffuser refills can be used only with Yankee Candle sleep diffusers (sold separately).