Add 2 cups of water into a 6 quart slow cooker. Then put liner on slow cooker. The water should not be inside the liner. The water should be on the outside.
Put sugar into a sauce pot and turn heat to medium high. The sugar will start to melt and turn into caramel. Stir as needed and be sure not to burn. The caramel is done when it has reached a orange golden color. Immediately remove from heat and allow to slightly cool for 2-3 minutes.
Pour caramel into slow cooker so that it coats the bottom of the liner.
In a separate large bowl mix together egg yolks, condensed milk, ¾ cup evaporated milk, water and vanilla extract.
When everything is fully incorporated pour egg mixture right into slow cooker on top of caramel.
Line the top of your slow cooker with a few paper towels to absorb any excess moisture. Be sure not to peek into the slow cooker and release any heat. Leave it closed for the full 2 hours.
Cover and cook on high for 2 hours. The custard is done once the outside are firm but the center still giggles. Return lid after checking then turn slow cooker off and allow custard to remain for another 30 minutes. This will prevent the custard from cracking.
Remove custard by lifting liner. Place onto a cutting board or plate then put another plate facing down on top. Gently flip onto plate pouring all the caramel on top.
Serve as is or with fresh berries.