While section hiking the PCT the past few weeks I observed a number of thru-hikers with Sawyer Squeeze filters attached to rigid soda/water style bottles.
It seemed pretty simple; no separate scoop, no need to unpack/empty a cook pot to scoop, and easy to retrieve, drink from and replace on the fly. But I wondered how they dealt with 're-inflating' the collapsed bottle after a squeeze or two. After watching one hiker loosen the filter between squeezes to 're-inflate' the bottle, I thought there could be a better way.
A simple check valve of some sort seemed to be good start. Here are some pictures of a check valve added to a Pepsi bottle. It works well and doesn't leak.
Duck-bill valve taken from aquarium check valve:
Duck-bill valve installed in appropriate size hole drilled with unibit:
Bubbles from valve during re-inflation:
Link to video: Windows Movie Format
Apple Quick Time Format
With the valve installed near the bottom of the bottle, the filter will even slowly gravity feed. (Gravity feed doesn't work well with the valve installed near the top, because head pressure inside the bottle keeps the valve shut.
Hope this is interesting and helpful.