Yes, putting foil in a bread toaster can ruin it and is not recommended. The reason for this is that foil is a metal, and when it comes into contact with the heating elements inside the toaster, it can cause a short circuit or spark, leading to a fire hazard.
Toasters are designed to toast bread and other similar items safely. They rely on the even distribution of heat across their heating elements to toast the bread evenly. When foil is introduced, it disrupts this heat distribution and can cause the toaster to overheat or malfunction.
Additionally, the sparks generated by the foil can potentially damage the interior of the toaster or cause permanent damage to its electrical components.
To avoid any risk of fire or damage to your toaster, it's crucial to keep metal objects, including foil, away from the toaster's heating elements. Stick to using the toaster for its intended purpose with bread, bagels, or other toaster-friendly items.