I can hear you now, "Who the hell finds scrubbing a toilet enjoyable?" Okay, so maybe you can't find the actual job fun and exciting at all times, I get that. Yet at the very least you should find some pleasure in doing a good job.
Take pride in what you do. At times, easier said than done, but if done at all times you'll probably find life at the station easier. The guys you work with are watching you, and how you handle these duties. Lets face it, if they can't trust you to mop the floors, how can the trust you in a burning building. If you work hard at everything you do they'll see that, and though they may still give you a hard time, you'll earn their respect over time.
Another reason is just for your personal satisfaction. Again, everyone at the station will know your work ethic and maybe, JUST MAYBE, someone will crack and give you praise for a job well done, and as a probie getting any praise is worth all the hard work. I don't care who you are, everyone likes to hear they did a good job. Especially when you do take pride in what you are doing and put forth effort.
After you see that working hard has plenty of benefits you'll take more pride in what you are doing and eventually maybe learn to love the little jobs given to you. If nothing else, these probie tasks are ones that every firefighter before you has done. It's a part of the life in the career and its one of the best careers out there. The kind of career in which you could be sweeping floors one minute and racing to a car wreck to save a life the next.