I sing a three hour session of Rock and Blues twice a week which is pretty hard on the voice, putting it mildly.
Is your throat sore the day after a singing session or does it start out that way? Very important to know because; beer, lemonade, orange juice, anything cold is adefinate no no both before and during vocal performances. Iced water is also a no no. Drink plenty of room temperature water only both four hours before a performance and copious quantities during a performance. Your tone, control and vocal stamina with improve at least 20%.
I make my living with my voice, trust me, this works.