Q.reusing sap for plant food
Can I use sap (amaryllis) mixed with rainwater and reuse as a plant food? Getting ready to cut back amaryllis after flowering and there’s a lot of sap in the stems – pity to waste.

I would advise against doing this as sugar water (sap is predominately sugar) can also attract other organisms and bacteria. In addition, every plant already produces the sugars it requires through photosynthesis. That fine balance could be disrupted by giving the plant more than it needs, which could be harmful to the plant.

You could certainly try this as a natural fertilizer.
Here is a link with some more information.
http://www.ag-usa.net/g_Chemical_Fertilizer_vs_Organic_Fertilizer.htm