You can use 2 liter soda bottles to carb and serve. No need to do anything silly like keep them on their sides or anything weird like that.. just....
1. Keep them out of the light because brown bottles filter light rays which cause hops to taste skunky and sorta gross. Clear plastic does not offer this protection.
2. Pour BIG glasses because every time you tilt the bottle back and forth, you will stir up more yeast, making each successive glass more cloudy and yeasty than the one before. Unless it's a hefeweizen that is not a good thing.
3. Just buy some beer and make yourself some empty bottles already. Sheesh. Do you really even need an excuse to drink more?