I use a cut off Clorox bottle as a scoop and the horse will drink out 
of that.  He will also drink out of anything if he is thirsty but I 
haven't tried a bottle or a soda can!  We have used collapsible 
buckets and its best to have both.  With the scoop you can get water 
out of shallow spots.  You can also use it to dump water on the 
horse. With the collapsible bucket you can lower it into a stream 
that might be hard or dangerous for you to get down to.  We've tied 
two tailing ropes together and lowered a bucket 15 feet off a bridge 
to get water.  We also used it at a canal that had fencing on both 
sides.  Both items are very handy!
I've never used a spritz bottle but it sounds like a good idea.  I do 
dump any extra water that I can on him.  I've seen the "Cool Offs" on 
horses but I haven't tried them.  They do look a little goofy but 
maybe they help.
Judy Long
Hayward, California