Gurobi Instant Cloud allows you to perform administrative commands (to abort a job, change the job limit, etc.), but you'll need to retrieve the administrator password to do so. The administrator password can be retrieved from the Instant Cloud Manager. For a running machine, you will find the administrator password in the Machines area, within machine details under the PASSWORDS tab. If you have no running machine, you can find it in the Settings area, under passwords settings.
For example, you can abort a specific job:
> grbcluster --password=XXXXXXXXX abort 3545d9de-8de4-4666-9491-5d60e2e56186
Or, you can set the job limit of a specific Compute Server node:
> grbcluster --server=ip-172-31-62-109 --password=XXXXXXXXX config --job-limit=10