Never, never, never withhold water from any chickens ever, ever, ever. Sometimes what you read is wrong. There is never a situation that calls for withholding water.
Withholding some foods may be necessary. You can give the chick feed as long as it isn't seeds or corn that require grit to digest. Also, any cellulose type vegetables must not be given during crop disorders. But water is nescessary to keep the crop and gizzard well lubricated. It will help in clearing up the blockage.
Do you have grit? Grit is small gravel that chickens and birds scratch up and swallow for their gizzards. Giving grit can also help break up the blockage.