But Lewis maintains putting his squad through further adversity will bring his team closer together before the World Cup kicks off in August.
He said: "It was about people appreciating other peoples efforts, pulling together, showing real team spirit.
"Those things transfer to rugby and we saw a load of that this weekend and it really has brought us that much closer together.
"There were a couple of objectives: we wanted to enjoy each other's company, we wanted to face a bit of adversity and we wanted to have some internal competition.
"That was a challenge that we all rose to and I think it ticked all those boxes."
The squad were put through their paces by Lance Corporal Chris Long from the seconnd Battalion, Royal Welsh.
And after making them suffer for a period, Long is confident the squad will be able to cope with whatever world champions New Zealand throw at them in the group stages.
He said: "Obviously when they're playing rugby they need a lot of endurance and a lot of stamina, more importantly they need to work as a team.
"We were putting them under pressure by throwing them in rivers, making them go up mountains so they're working as a team to get these tasks done which is exactly the same as on the pitch.
"They've got to achieve a goal working as a team which generates that teamwork under pressure to be able to apply it to a sport.
"Everyone pulled together, worked hard, pulled everyone through, picked up a couple of injuries but we worked around them, everyone did really well."