2001 GMC Savana 5.7 liter sfi dual battery drove to ny and back to fl fine. Shortly after came out tries to start not at at to statt. Fpund alt. To be bad. Replaced it ran fine.bit squeling changed tensinor pully kept squeling. Found the to be fan clutch. Replace it. Still did it found out auto zone gave me wrong part. Changed alt to right amps. Still died by morning. Took to shpp number 2. Guy said he checked everything and nothong was drainging it or he could not find it. Took to aamco. Ran dio. Foind alt bad and batteries bad changed batteries and took alt to expert said that voltage reglator was bad. Reppaced said everything was fixed gqve us van back $1000 dollars later said it was fine started and ran fine all day batterie meter was fine . Went to start it that night not enough juice to crank that time dont know whats draing plz help

put a meter on the battery, see what the cranking voltage is. could be that the starter cables or starter is going.

Do you have any after market accessories installed? Is the radio original or a replacement?

Sounds like you have a parasitic drain, give this a read.
https://www.gmforum.com/trouble-shoo...w-test-293647/

If you need a video I found an ok video, it actually touches on some important things, like not opening any doors, or turning anything on when testing for amp draw.

If your battery is constantly dying, and getting dead cells, needing replacement, then until you chase down the draw you have, you could use something like this, it is a great battery maintainer, it should compensate enough for the draw, that your battery does not go dead.

parasitic drain test is your best option currently.