The story of Nirjala Ekadashi is something like this, which is known to us from Mahabharata, that all the Pandavas used to observe the fast of Ekadashi, that too Nirjala. But Bhima could not keep this fast.
Once Bhima asked Vyasdev ji that he cannot starve, he can do charity, chant, listen to Bhagwat Katha, worship God with devotion and law, but without even a single time It is not possible for them without food.
Because his another name is vrikodara, vrik means fire and udar means stomach, so there is a fire called vrik in his stomach, to calm which he needs more food.
They have the strength of ten thousand elephants, and they do the same work, so they need the same food. He is the son of Vayu, so he cannot observe Ekadashi fast.
Then Vyasdev ji told him about Ekadashi and said that there are two Ekadashi in a month, and every person should observe both of them.
Hearing these words of his, Bhim said impossible, if enough is enough, I can fast once a year, so you tell me about such a fast by which my life will become auspicious.
Trembling with fear, Bhima said to Vyasdev ji, please tell me about such a fast, so that I can get the fruits of all the fasts.
Then Vyasdev told about Nirjala Ekadashi of Shukla Paksha of Jyeshtha month and told him that, by observing it one gets the fruits of fasting of all Ekadashis, but do not even drink water in it.
Bhima was very pleased to hear this, and he duly observed this fast, and hence this Ekadashi is also known as Bhimseni Ekadashi, or Pandava Nirjala Ekadashi.
On this day listen to the Lord's beautiful pastimes as much as possible, read the Bhagavad Gita, and chant the Hare Krishna mahamantra as much as possible. Hare Krishna Hare Krishna Krishna Krishna Hare Hare Hare Rama Hare Rama Rama Rama Hare Hare 🙏🙏🙏🙏🌺🌺🌺🌺🌺
Next day worship God by taking bath etc., and then feed the Brahmins, or donate food to them. Those who have performed Nirjala Ekadashi should first give water to the Brahmins and get them fed, then take water and food themselves.
Not everyone can live without water, so those who have the capacity can keep the fast by taking water, or fruits, and other ingredients of the fast according to their ability. Do devotion to God more and more on this day, and keep your mind engaged in the beautiful name, form, qualities and pastimes of God.