Boil water in a saucepot. Add sugar and stir until dissolved.
Add decarboxylated cannabis to the pot and stir gently.
Cover and reduce heat. Let simmer 30 minutes.
Stir in vegetable glycerin. Reduce heat to low and cook 10 minutes.
Turn off heat and let mixture cool.
Strain mixture through a cheesecloth or nut milk bag suspended over a mixing bowl. Let sit for about 30 minutes to drain.
Squeeze the solids to extract every last drop of syrup.
Store syrup in a tightly sealed glass container in the refrigerator OUT OF THE REACH OF CHILDREN. Lasts up to 3 months.