I apologize for this giant wall of text, and this probably doesn't count much towards 'general advice' since general is usually short and sweet... but if you choose to read all of this I hope it helps.

I don't know how long ago you started to eat healthier and hitting the cardio, but be careful. It sounds like you're treated your body to a lot of garbage over a lengthy period of time, so jumping into a sudden healthy diet and intense cardio regiment could cause some problems since you wouldn't be used to most of the changes. A couple years ago when I decided that I wanted to live past 40, I hit the gym, cut the bad foods and spent time walking/running (or tried to)/biking. I'll never forget the feeling of horrible nausea/headaches/fatigue from doing a moderate amount of work for the first week or two.

You mentioned that you dropped soda and fast food ~2 days ago. At this point your body would still be used to high sugar/fat/caloric intake and low nutritional content. Drinking 2L of water instead of Coke is a great start, but pace yourself on the exercise. From what you've described, you're looking for a 'quick fix' by leaping into over an hour of cardio for your first time back. You're not going to lose ~15-20 BF% in a couple weeks. It will take longer, depending on a majority of your diet/exercise and the rest being mental.

(Now, I'm probably no where near as experienced as most of the people on these boards, but I do have experience on weight loss.)

I'm 22, 6'2" and at my embarrassing peak I weighed 305 lbs at close to 32 BF%. 8 months later, I'm down to ~230 lbs at roughly 11-12 BF%. To achieve this I dedicated about 1.5-2 hours, 5-6 days a week weight training for the first portion and then walking on a treadmill for the rest of the time (3-3.5 speed, increaseing the incline). Since I was fairly lazy, I found that circuit training/super setting allowed me to maintain a 120-130 heart rate going into my 20-30 minutes of daily cardio.

Now, I mentioned a mental aspect. You have to realize that there is NO quick solution to weight loss. This will take time, depending on how much effort you put into it. Find some sort of motivational factor. It's crucial. Use it everytime you find yourself asking yourself why you're doing this, or when you think about skipping days/breaking your diet for whatever reason. Goals are also important, make reasonable short-term goals and work towards them and then progress to longer-term ones. It puts you in a better mindset when you feel good about accomplishing something you've worked towards. Don't get discouraged if you don't make your goals either. Try and find out what you could've done differently and adjust.

I've tried a lot of diets, including starving myself. You first need to find a diet that works for you. No ONE diet works for everyone, despite what the TV says. Start off with cutting down on portions and substituting in vegetables. Drink lots of water between meals. It will help to manage your cravings and it's great for you. Lastly, don't feel bad if/when you binge and indulge yourself every once and a while. It can help as a motivational tool depending on how you use it.

Exercise will ultimately be the best lifestyle change. You can only go so far with dieting. Commit yourself to the treadmill/bike and find something that passes the time.If you find yourself looking at the time every 30 seconds you're eventually going to try and convince yourself that you can sacrifice time and/or certain days to skipping cardio (This was the toughest part for me, but it sounds like you've got it handled). If you turn your experiences on the treadmill/bike into enjoyable ones, the easier this will ultimately be. If you find it fun, you can then move cardio to everyday life and not just 'gym time'. Finally, I'd recommend possibly getting into a routine of doing Squats, Dead lifts, Pull-ups (or assisted), Benching (go easy for the first bit if you're not used to this type of training). If you work on your larger muscle groups, the easier it will be to eventually lose weight because the more energy they will require. Especially since you're using most of those muscles when you're on the cardio machines. Not to mention those exercises will also bring your heart rate up and usually keep it up depending on how long you rest.

And finally, knowledge is power. Do your research. Read various websites on nutrition and exercise and use more than one website as your reference.