As long as the fuel is sealed, any condensation on the inside of the jug is just fuel that has evapourated in the jug and condensed on the inside.
I'll second that! In fact that is exactly how you distill alcohol from wine. Both meth and ethyl. You will see the same from a new bottle of fuel. If any doubt get a new bottle of unopened fuel and set it next to the old. Wait for it to reach the same temperature. You will see condensation on the new fuel. Our fuel is almost as clear as water, the oil is what has color.