How do you feed lizard when its too weak to eat?

Try feeding it something it can eat through a syringe, such as baby food. Do not feed it a lot, and add a little water. Take care to allow it to swallow.

Depending on the type of lizard it is, it may be hibernating and has shut down for that reason. If it is not skinny, leave it alone.

The third option is to take it to the vet.