Similar rides in the past I've carried ~3 quarts and never used it all, distances 60-75 miles - including riding a non-ebike. I also carry a water filter and some purification tablets, the chlorine type, not iodine. Iodine purifiers make the water taste bad and it doesn't seem to quench thirst as well either.
I was hoping to go for the last couple weeks but weather hasn't cooperated. Next week temps forecast in the 90s so hoping for more moderate temps week after next.