Banannas are rich in potassium
Eggs are rich in phosphorus
half of ea per gallon.
The nutes plants like are also very good for humans too. There are TONS of household foods that are loaded with NPK nutrients. Eggs and banannas have really high amounts of PK and are the easiest to work with.
You could also use almonds, whole grain bread, etc and mix it up well in your soil. Just google "High phosphorus/potassium foods".
You just need to make sure you strain your mixture thoroughly to insure there are no chunks of food sitting in the water.
People have been using regular food as plant food for hundreads of years, long before there were any of these synthetic concentrated blends. Banannas and eggs is one of the oldest tricks in the book.