In Oblivion, there is a scene in which Jack and Victoria are eating something that looks like meat.
From where did they get this food? The earth is contaminated with no apparent animals.
The Tet's mission is to check on the Effectiveness of the Team from time to time.
One of the factors of the "Team's Effectiveness" is the condition of its food source, or food inventory. If the team uses up all of its quota, then the Tet will initiate an order to eleminate the team.
This is explained in more details here:
I am sure that the Tet would utilize the entire ocean, setting up dozens, if not, hundreds of the water extractors. The murder-bots assigned to kill the teams if they become ineffective would shut down. Depending on the teams’ food source, many could die of starvation, dehydration, or from harsh conditions. Or they could be fine. Its all speculation.