I play hockey 4 or 5 days a week, and some high level competitive mens vball twice as well. No gym time for me (although I should, as I hit 40 all the injuries start to appear randomly).
Proper sleep and rest is key to energy I find, and second the coffee comment above. Sometimes I drink a hot chocolate (Wayne Train style) prior to hockey, or even a can of what you folks call "cola" down there lol. Anything to get the sugars up. A smoothie with fruit also seems to be a good alternative about an hour prior.
Life as a desk jockey hurts, the sports keep me in decent shape, but the gym is something I really should do as well for preventative purposes. When I did have a gym day in the rotation (about 2 years ago), it was H.I.T. circuit training using a TRX suspension trainer, jumping rope, wobble board, kettle bells and heavy ropes - great for strength, mobility, balance, etc. I was in solid shape with that one day a week in addition to the sports (diet was really clean also). If I start a proper "gym" routine, will base it on the TRX again for sure.