For this to work you must have 2 users (use the add manager function).

1 user is at the club you wish to control and the other is at a rich club (I suggest Chelsea as they start the game with 200 Million so taking 100 Million won't affect the game).

At Chelsea approach your other club with a loan offer for any player, at the offer screen set the loan fee to 100 Million, switch back to the other account and accept the loan, keep switching until the loan is agreed by both sides and your first team will be given 100 Million.

After completing the cheat retire as Chelsea manager to continue the game.

NOTE: You don't have to set the fee for the whole 100 Million it can be anything in between but if you are wanting 100 Million then I strongly recommend you take from Chelsea as taking 100 Million from any other club may alter the game too much.