Camel tanks ADV make an auxiliary tank for the AT. You gain an extra 100km but they cost around $400 US. At present they only have a tank that fits bikes without the pannier racks, however, they will be releasing another tank in the coming months. You might want to check out the high fender kits as well. I just purchased one! I wouldn't go with the pop bottles, that is an extremely dangerous practice and I have seen what happens when petrol comes into contact with a hot exhaust.
"Men do not stop playing because they grow old, they grow old because they stop playing."
O. W. H.