If you replaced your canteen with a nalgene bottle you'll probably want to aquire a cup to use with it to boil water in,
cook food and all the other things the canteen cup was used for.
They range in price from $8 to $60 depending on size and how light a cup you want.
Where I live there are no sporting goods stores around so everything cool has to be ordered via mail.
If you don't have the money, time or desire to purchase a nalgene cup you can improvise one out of a number 5 can for dehydrated food.
We all know what a number 10 can is, figure a can 1/2 that size. That is a number 5 can.
You can probably find some food in the gorcery store of the same size if you don't have any used in food storage.
This gives you a can of food and a free cup. Also it is much easier to put a lid on a round can then a canteen cup.
The can will hold about 3 1/2 cups of water. A similar sized nalgene cup is at the higher end of the spectrum.