How do I begin giving up sugar?

Lately I’ve been consuming a lot of simple carbohydrates and I’m starting to feel the effects. I know they aren’t good for me, but with my hectic work schedule, most days I don’t have time to cook a proper meal.

Every day, I start my day by eating a toasted Thomas’ everything bagel with Philadelphia chive and onion cream cheese and a cup of Post’s Honey Bunches of Oats with Almonds cereal with whole milk (I don’t like “skinny” milks). During my hour-long break at work, I usually have pasta (it’s the easiest/quickest thing I have time to prepare most days) or a frozen meal or, my least favorite, order in with the rest of my co-workers, which has been happening a lot more frequently than I’d like to admit. Throughout my workday I snack on little chocolate bars and M&Ms which are always readily available, courtesy of our secretary. By the time I get home at the end of the night, I’m starved and I end up stuffing my face with Stacy’s Pita Chips (the naked kind) and some juice and then I go to sleep feeling disgusting.

Weight is not my main concern right now as I’m fairly on track with where I want to be (I’m 5’9” and weigh 150 lbs), though I could stand to lose some tummy flab. My health is my biggest worry because I’ve had nutrition courses and know what will happen if I keep eating this way. I used to work out 5 days a week, but I’ve been slacking off for the past month or so, again, because of my work schedule. I’m still pretty active as my work requires me to be constantly moving (except on the days when I work in the office and have to sit in front of a computer for about 8 hours) and I also walk at least 30 minutes each day.

How do I get back into the habit of healthy eating considering the following obstacles?:

1) My work schedule.
2) I don’t own a car yet – I go grocery shopping with my flat mate every other week and I have to buy items that will not go bad easily, which leaves out a whole plethora of fruits and vegetables.
3) I may be addicted to sugars because I crave them constantly.
4) People at work are always ordering in and/or offering to go out and get food for all of us and I can never say no.

Help!