Companies are required by law to reduce working time by 2 hours per day for all employees, not only Muslims. If employees work longer hours, they should receive overtime pay. Workers can file a complaint at the UAE Ministry of Labour if a company is not following this rule, or not paying overtime for employees who do work longer hours.

It is illegal to eat, drink or smoke in public during daylight hours (including in your car). Urban legend has it that you end up in jail for the remainder of the month of Ramadan if caught (the law says a fine up to 2000 dhs or a one-month jail sentence as far as we know), however it is more likely that you'll get a lecture from the police and possibly a fine.

For example, in September 2008, a Lebanese male resident and Russian female visitor were drinking juice in an EPPCO petrol station in Dubai before Iftar, and fined 1000 dhs each according to an article in the Gulf News. Apparently a witness saw them and reported them to the police, who shipped the couple off to court. It seems a surprisingly harsh outcome, unless there is more to the story than was reported.
Sharjah is likely to have harsher penalties for the same offence.
It is respectful and polite to dress more conservatively during Ramadan - shoulders and legs should be covered.

Bars in Dubai are usually still open but patrons will be asked what religion they are and refused entry if they are Muslim. Live and loud music is banned, so is dancing. Bars in Abu Dhabi might be closed. Bars in Ras Al Khaimah stay open. Bars in Sharjah don't exist.

Any alcohol related offences will probably be treated much more severely than outside the month of Ramadan - it is quite possible an offender is stuck in prison until the end of Ramadan.

Car stereos should be turned down - loud music, especially rock or similar music, is disrespectful at least, and if police hear it, they'll have something to say about it.

Traffic jam times change - the morning is not much different but afternoons from 1300-1600 is quite busy, and again just before Iftar as many people are trying to get to a desired location for Iftar. Every year there are numerous accidents and requests from police to drive carefully at the time. For an hour or so just after Iftar, and from 1600 to an hour or so before Iftar, the roads are relatively traffic-free.