this is a guaranteed winner
A new pop bottle
Eat your heart out you, you, you ... commercial designers ... arrgghhhhh
Bear in mind that this is for a 20oz or 24oz maybe as low as 16oz but not a 12oz and not a full liter. The design is not finished and requires some bit of work so that it's strong enough, i.e. a little research. But you can see that the idea would be an immediate winner ... especially in the summer when you want to take your Pepsi or Coke with you ... but ... you want your hands free too. Also, after you're done you can use it for a canteen and, if the manufacturer is not stupid, the name of the company will be on the plastic so that you can't take the label off ... thus making it an advertising message even while carrying only H2O.
It is under pressure and the walls have to be thin to keep it cheap ... so ... it must still be radially symmetric looking from the top.
Only the cap holder would cost a bit more (it's been done before) ... but the holder isn't really necessary and could be omitted with no loss in sales.
The finger hold must be experimented with for fit so that it feels "sexy". And the thumb ridges need to be worked on to feel sexy too. It's a non-slip feature. Maybe they should be vertical. You see the way it goes on the belt so that it will hold well and requires that the belt be bent a little to get it off. Again, this needs some research to see what feels good ... a combination of holding firm yet must come off easy to drink.