Just had to share a great idea. Check out this great usage for water bottles.
Cut off the top of a water bottle, tossing out the bottom of it and keeping the top portion with the bottle cap.
Remove the bottle cap, then take your bagged leftover anything such as rice and thread it through the bottle top, fold over the bag, screw the cap back on and voila! You have a tightly sealed container without having to find a twist-tie to use. Best of all, unscrew the cap and you can pour out the contents quite easily.
Hint: I think you want to use a soft, flexible bag rather than something stiff like a potato chip bag.