Now that I am out of the cup and only have about 1.5 game per day, it's not an issue. While I was in the cup, it took me about 4-6 green packs a day to maintain both max bonuses (10% across the board) and fresh troops. Now I only need 1-2 green packs per day.
There are two reasons your players are exhausted.
One, you are using high pressure and/or man-to-man during matches. I only uses those as exceptions when I feel I will lose without them. Each of those options use a lot of condition. Perhaps 30% more, I am not sure, maybe someone knows. Combine those and your guys will be knackered for the rest of the day. Mine recover in about 6-9 hours enough to either play again or train.
Two, you have not figured out the optimal drill sets to maximize bonuses. This is one of the challenging parts of the new system and a closely guarded secret.
Personally, I found a drill set that gives me 3+2+3+3 bars bonus for -7.5% condition burn for 8 players. I have tried to improve it to either 3+3+3+3 (max) or smaller condition burn, but every time I touch even one component, my bonus goes to hell, so I don't know if it can be improved. Sooner or later threads will surface where people will reveal, rather than brag, their best combos, until then everyone is on their own.
Once my Condition bonus is at max 10%, I start training in fours, boosting the remaining bonuses, hopefully, by 3 bars at a time. Once all bonuses are at 10%, I can afford to give individual attention to players who still have high condition and pick training regimens that address their needs rather than boost the bonus.