>>877123You won't get sick off it, but you could improve the basics of what you're doing for a better and more consistent brew.
Sanitization - you didn't mention doing anything to sanitize your coke-bottle fermentor. Like I said, it's extremely unlikely that you'd get SICK, but bacteria that will make your brew taste bad can easily hang around on surfaces and grow in a fermenting liquid. There are some no-rinse sanitization products that make this easy, or if you're on a budget then you can just use a bleach solution:
http://homebrew.stackexchange.com/questions/5837/homebrew-sanitisation-in-a-pinchYeast - you should get ahold of some dry brewer's yeast. A lot of it is basically just as cheap as baking yeast, but it's designed for brewing. There's beer yeast and wine yeast, and a lot of different strains of each, all with different properties... but generally they affect the flavor of the brew less than bread yeast does, and they flocculate (sink) better. So when you try to separate the brew from the shitty dead yeast and gunk at the bottom, it's easier to do so when you use brewing yeast, and the final product is clearer.
Time - A week is too short - your brew might still be fermenting a little bit at that point. Ideally you would use a hydrometer and would know it's finished fermenting when the gravity is stable, but practically you can just give it like 3 weeks, I usually give my beers about a month. Fermentation is usually done within a week or two, but it's good to give it some time for all the yeast and crap to fall to the bottom, which will result in a clearer product. Past that, if you bottle it, it will taste better after given more time in the bottle. Brews change in flavor a lot in the first few months of aging.
The balloon thing is fine (airlocks are better and are like $1), but sealing and unscrewing the bottle could make a messy disaster if you forget to do it for too long.
