I like to go camping and I frequently use small PET soda bottles as sealed containers for sugar and flour etc. The problem is that these bottles have a wide opening which makes pouring stuff out of them a hassle. That is why I designed these inserts that acts as spice caps. If the cap of the bottle is tall enough it can be screwed back on the bottle to seal it off.

You should try the short one first since it usually fits pretty well.