Been in the Army, but never drank that many energy drinks...so I'm not sure if I'm eligible to answer your question but here goes...
The Army definitely changes you! But, that organization seems to breed a very high level of loneliness! Why do you think the bond and camaraderie is so strong between soldiers, marines...The loneliness factor is a big contributor to that. He may want s*x, but I think he desires the idea of you taking loneliness away.
Maybe the energy drinks were to replace the calories spent on a demanding road march or PT test. I've seen soldiers go over board when their bodies are spent.
I think he is being honest with you. You might want to check to see if its really YOU who he wants to be with and not just someone who can help him get over him being lonley. Hope this helps and good luck to you and the soldiers. Soldiers make outstanding lovers! They are always at the position of attention.