I used a 3/8" drill. Yes, it is a gatorade bottle_still waiting for diet gatorade (which IMHO is silly, let's have a energy drink with sooo much HFCS High Fructose Corn Syrup that we need a diet version.
In one month, I've had to recharge the bottle 1 time, due probably to my stupidity. I added baking soda_not smart.
Right now, I take a teaspoon of sugar and add it to about 1" of warm water in the gatorade bottle. When the sugar has dissolved_if you can't make the sugar dissolve, add a small bit of warm water. Then I add 1/8 teaspoon of active yeast_I don't refrigerate the yeast after opening, contrary to instruction on package.
I give it a shake in the AM, and then throughout the day, I keep an eye on the bottle. As long as there are bubbles forming and breaking there is co2 being produced_I don't know the levels. If no bubbles, give it a shake. When the bubbles eventually stop, I first add a small amount of sugar to see if that will start the fermentation process again. If not, then add a bit of yeast.
Hope this helped.