The Holding Tank (aka Fish Bowl, if the Tank is made up of mostly see through material). is quite different that from The (Drunk Tank). The Holding Tank is where every single "new" inmate waits while getting processed in to whatever jail or prison they will be living at.
The Holding Tank is a staging area for all inmates waiting for their Court hearing, (usually in big cells with one or more toilets).
A holding tank is a common euphemism that is used ambiguously throughout the jail/prison community. There are many times and many reasons that an inmate might be placed in a Holding Tank. i.e. in process, waiting for court, waiting to bail out, out process, and so on.
"Wow, we have been waiting for ever in this rotten Holding Tank waiting our turn to get fingerprinted"