After having my filter clog up on me in the middle of a backpacking trip, I was determined to find a better solution than the syringe. This is what I've come up with. (FYI, I have the older squeeze without the nipple on the outlet side).
I've always used the flip-top sports cap from a smartwater bottle, as I don't have to worry about using the lid. This makes up half of the the back flush.
For the other half, you just need one more smart water sports cap. Tear of the flip-cap and 'pop out' the blue center spout…. That's it, your done. When connected as in the photos, it snaps together to make a secure fit back flush with.



All for the cost of a bottle of water.
I now use a evernew bag to drink from, but it also worked when I used to use a smart water bottle.







