Although there are rumors of people being able to create Ful Bombs, food or water by using spells, it has never been proven to be true. Maybe very early versions of the game allowed that, but it is definitely not possible in any of the versions available on this site.
About creating Ful Bombs, Doug Bell said the following in an interview by Gambit: "We originally included the spell, but then realized that since the spell destroys the flask that someone could inadvertently use up all their flasks. We worked hard to protect players from creating unwinnable games."
That spell could have used the Gor symbol which is not used in any spell in the final game, and which description in the Dungeon Master manual would make it a perfect candidate for such a spell.
Note that the Poison Potion (Ven Potion) spell also destroys flasks.