Saccing is short for sacrificing. You can sacrifice items in an altar to restore spell favor quickly.

To get a sacc value of an item, right click it and Get Prices. It will tell you how much favor it will restore.

You can also use the Favor Calculator but you have to set it correctly according to the item or you will not get the correct value. For example, the default setting for the mod is 1.0 and tells you that a chopped cabbage of 99ql will give you 20.00 favor, but this is not correct. If you set the mod to “favor 0.2” then it gives the correct amount as per the Get Prices, and thus the cabbage modifier is 0.2 which is used to calculate 4.0 favor.