If you mean that it is a checkbox field, then you really can’t do what you want to do as far as sorting.
You would need to use something like a repeater where each row allows selecting 1 type of grape and setting a percentage and then you’d need to build functions to sort the rows of the repeater in the correct order based on the % sub field.
You could do it by having a conditional field for each grape type that is shown when that type is checked to allow entering a %. Sorting the grape types by this value would be more difficult because each would be in their own field.
Without a repeater there isn’t any way outside of the code you right to associate one field with another field.