Straw exercise for the tired voice:
https://www.youtube.com/watch?v=0xYDvwvmBIM
https://www.youtube.com/watch?v=FStqHThEY9M&t=47s
https://www.voicescienceworks.org/straw-phonation.html
Tips on Vocal Health:
http://www.lionsvoiceclinic.umn.edu/page4.htm
Interested in the anatomy of the vocal tract? Here you go:
http://www.lionsvoiceclinic.umn.edu/page2.htm#anatomy101