How did they make plastic?

How to make small hole in plastic tub for my hamster?

• This may be a little long but please read all before answering. Thank you. I bought a shelves with plastic tubs to keep my hamsters in. But the tub is a good decent size for them and there is room for the house, wheel, and bowl for food but the water bottle is to big and will take to much room. I buy the 16 oz bottle because its 3 dollars and the small ones with a holder are like 7, so I save money, but I want to make a hole in like 1/4" so I can put the melt part of the bottle in the tub and the bottle outside to give the tub space. I don't want to mess up the tubs, how can I do it without making it crack or coming out to be a uncircle like hole. I don't want to cut it to big cause then the hamster will chew the plastic but good size so i can squeeze it in and let the hole be tight and not loose. I don't want to do the burn a melt stick to make the hole because it will make the plastic around it weak and my hamster will probably chew on it easily. If there is a tool meant to cut holes in plastic without messing it up that you would recommend, let me know and tell me the price of which it might cost me. I really needa do this right.

• Answer:

  a boxcutter.....the blade is very sharp......they are pretty cheap, you can get them at any hardware store or walmart or wotnot.........