It will work. I a 2L bottle set up like this on my grow out tank.
I wouldn't use silicone though. Just drill the hole in the lid small enough that the tubing is very tight. I've been reusing the same cap on my little grow out tank for half a year or so.
Airstones aren't a very good way to diffuse either. I suggest a split impeller powerhead and lift tube, or alternatively, you can plumb it in to your filter intake.
A 2.5G aquarium is very small, so you may want to go easy on the yeast and sugar. I'm just guessing though. I haven't tried this method on anything under 10G.