16oz water bottles would probably fit between the levels, but the problem would be getting the nozzle though the 1/4" hardware cloth. You'd have to either ream out a spot or clip a few wires to get the sipper tube through for the mice to be able to drink. With a bottle that small, you'd also be changing it pretty often. I use 32oz bottles on my rat racks, but I've got to change them every couple of days. One of these days I plan on converting them to PVC and sipper valves but I haven't found the time yet.