Justin,
You can miss your meal, work, school and all other worldly things, but you cannot miss nitnem even if you are sick. It's our spiritual food. I would say exception would be when you are unconscious or have mental incapability due to illness or accident. As soon as we recover, we should catch up to our nitnem. Remember, nitnem helps us clean our ourselves internally, get spiritual knowledge, and makes us sing praises of Vaheguru who will save us in this life time and after. Nitnem is gift given to Sikhs by their Gurus. So why question?
If you do not have access to water, Guru ji will understand. However, you should make every effort to take shower before doing nitnem in the morning.
Vaheguru Ji Ka Khalsa, Vaheguru Ji Ki Fateh