Egypt’s final preparations for the World Cup this year fall under Ramadan which began on May 17, and is due to end on June 14, the day when the World Cup kicks off in Russia.
During the month of Ramadan, Muslims are restricted from eating and drinking from dawn to dusk.
The Egyptians are however yet to decide as a team whether to continue observing Ramadan.
But Cuper has already expressed concern about the effects fasting could have on his players when the tournament begins.
“Fasting is the most important issue now, I am afraid that it could badly affect the players at the World Cup,” Cuper was quoted as saying by the BBC.
“I don't think the travelling during the friendly matches will leave them exhausted, I'm just trying to prepare them well for the matches.”
Liverpool have already confirmed that Egypt star player Mohamed Salah will not fast in the build-up to Saturday’s Uefa Champions League final against Real Madrid. Though, he is expected to fast before the World Cup.
At the last World Cup edition in Brazil, Ramadan also affected the tournament, but fasting Algerian players managed to stretch eventual champions Germany into extra-time during the last-16 round match which they however narrowly lost 2-1.
It is not yet clear if Tunisia, Morocco, Iran, Saudi Arabia and other World Cup teams with Muslim players will allow their players to observe Ramadan.
On Friday Egypt will play Kuwait in an international friendly match before other preparatory matches against Colombia on June 1 and Belgium on June 6.