There are two different saps you can purchase from the Fairy Forest.
Willow Sap (below) is a blue droplet that costs 1 pass. It will restore your baby's wellness gauges back to 100%.
Lotus Sap is a magenta droplet that costs 1 pass. It will return your baby's development to an average level if he/she is falling behind. This item will have no effect if your baby's development is average or above average.
NO LONGER AVAILABLE!
How to Use EditTo use the any of these items, simply click 'Use' on your baby's console page, in the notebook. The sap will restore your baby's wellness up to 100%, development, or weight, depending on which one you use. Some players may use the Willow Sap, because it makes their baby's growth and development increase faster. Also, it may be important to use the sap if your baby is in very poor condition, because you didn't put them to bed properly, or didn't take good care of them, and you may not feel like feeding, cleaning, playing, and napping your baby to raise all of the bars up.