We have a bottle attached with self adhesive velcro which you can buy from most craft stores. Your need to use a mouse bottle though else it is too heavy and stick a whole strip round the bottle then a good bit on the tank wall.
You can also get metal hangers that clip over the edge but these don't sit well if you have a fitted tank lid. You can also get free standing holders or just hand the bottle swinging off the roof. This actually works fine! They don't chew the spout then either as they cant get a grip on it.
We hate sippy bottles! We just use the colourtone bottles and find them fine. You can actually use the sippy frame and just put an elastic band round the bottle and accross the two outside supports and it will do fine