Making soda with yeast It is easy to make soda by adding sugar and yeast to a bottle of water and closing it tightly. However, checking different recipes, I did not get what is the best condition for this. I have a couple of tiny questions to find the optimum treatment.

I added 1/2 tsp instant yeast (baking yeast) and 1 tsp sugar to 2 l of water.


Should the bottle left untouched, or it is useful to shake it
occasionally? 
To keep it warm, is it good to put it in sunshine, or
    a dark place is better for it?
Leaving air in the bottle or filling it completely?
I agree with @SAJ14SAJ. What I would add is that


yeast does not require sunlight in any way ... but as UV light can be harmful to microorganisms and might inhibit yeast growth I wouldn't brew it in direct sun.
for bottling beer it is normally suggested to leave the correct amount (1 - 1 ½ inch) of headspace (air) at the top of the bottle for carbonation and proper pressure. But I am not sure if the same conditions apply for soda - I would think it is not too different.
shaking gently occasionally might help to evenly distribute the yeast in the sugar solution, and expose it to more food resources (sugar).