Experimented a bit with different water qualities when drinking. Values are per sip (0.05 liter)
Water 10/10/10 Stamina: +10 Energy: -20
Water 10/37/30 Stamina: +10 Energy: -16
Water 10/12/29 Stamina: +10 Energy: -17/18 (saw both numbers over multiple ticks)
Water 57/38/10 Stamina: +10 Energy: -15
Hot tea 52/43/50 Stamina: +10 Energy: -5
Hot tea 52/46/50 Stamina: +10 Energy: -4/-5
Hot tea 58/46/48 Stamina: +10 Energy: -4/-5
Cold tea 52/43/50 Stamina: +10 Energy: -14/-15
Cold tea 52/46/50 Stamina: +10 Energy: -14/-15
Cold tea 58/46/48 Stamina: +10 Energy: -14/-15
So it looks to me that either substance or overall quality affects energy drain when drinking, and nothing changes the stamina gained.
Anyone got any other observations or guesses on the formula?