We should ideally be resting while doing a fast. However, if you have to go to your office, then you can do the following:                                         

1. Take fresh coconut with you and have its water in the office. 

2.  Find a vegetable juice vendor near your office. 

 3.  If the above two options are not suitable, then you can take vegetable juices to your office. However, we recommend having your juice within 15 minutes.