I modified @timogiles' excellent six pack holder for 8 bottles, as my favorite soda maker sells in 8 x 8 oz bottles. Attached here in both sizes. The original holes were for 12 oz. bottles, and the holes were about 2.75" in diameter. (leaving a 1/4" total gap?) The 8 oz. bottles are 2.25" in diameter at their largest, so I made a version with 2.5" holes for the 2.25" bottles. The diagram with "both" has both sets of holes, concentric, and you can just cut whichever works for you.I opened up the 6-pack design in inkscape, expanded for two more bottles. Used lots of guides to make it easier. The original had a bit of space where some parts went through other parts: I kept the space on the outside edges, but tightened up the internal slots to give it a bit more stability. I assumed 1/8" baltic birch plywood (.118), and all slots are cut right at 1/8" (.125). I originally built this so I could engrave a friend's logo on it, to use as a show piece.