Can you use the 5 gallon bottles they put water cooler water as fermenters?
Tried that with a plastic one a long time ago. First batch went OK, second was infected. The inside of the bottle was not smooth so I think it was not possible to get it completely sanitized. No rinse sanitizers have improved since then so you might have better luck.
What you buy from a homebrew store for a glass carboy might be a water bottle.
I’d spend the little extra money to buy a 6.5 gallon glass carboy or better bottle.
OR, you can just buy another bucket from your LHBS and that would do just fine.
Your cost would be less than having to replace an infected batch of beer.
Don’t take any chances when it comes to having your equipment completely sterile!
try going with a “better bottle”, just don’t scrub it…buy some PBW cleaner and follow directions or ask how to use it.
i use glass and better bottles and leave the glass for super hot ferments, or when I don’t have to move it far.