Infant fever 7 months old. It could be from teething. But do I do. And can I give him water and how much?

Doubt teething. Historically teething has been blamed for many symptoms but in reality most infants cut teeth without significant consequence. Fever greater than 100.5 is most likely related to a viral infection and could be treated with Motrin or tylenol (acetaminophen). If fever persists for more than 3 days or your baby has persistent inconsolable crying he should definitely be seen. 1-2 oz of water in a sippy cup is ok.
Pediatrician. Have your pediatrician diagnose the fever source and i think that water is ok to the extent that the baby drinks it.