Yesterday afternoon when I came back from work I cooked some boiled egg for Baru. He was sleeping under some tissue paper in a corner of his cage, and when I put the egg near his head he woke up (most likely because he could smell it) and started eating small bits of it. After that I took him in my hand and gave him four or five drops of milk, then put him back in his nest and he went to sleep. I also put two small slices of cucumber close to his nest in case he woke up.
Around two hours or so later I heard him moving. I went to his cage and saw that he had walked outside from his nest and was biting at a slice of cucumber. He ate more than half of it (!). When he finished he just lied there sleeping, so I put him in his nest again and covered him with tissue paper.
Later I was reading at bed and heard him wake up again. I saw him still laying on his nest, but he was pushing the boiled egg with his nose towards the corner. He was also taking seeds from the hamster mix that I left next to him and was putting them one by one close to the boiled egg. I took him again and let him walk for a while on my bed. He walked a few steps, but got tired soon and I put him on his nest again. I noticed a small change in him, but in my opinion very encouraging: his eyes didn't look sad as they did yesterday.
This morning he woke up when my alarm clock went off, but he didn't come out from his nest. I took him, cleaned his back and let him walk a bit on the bed. He seemed to have recovered some of his strength. I put him back in his nest and came to work. Then, at lunch time I went back home to check him. He was sleeping, but when I put a bit of fresh apple near him he almost immediately noticed it, rose his head and started eating it. Then he went back to sleep and I covered him again.
He seems to be a bit better than yesterday, though he's still very, very weak. In any case he's eating well and getting liquid in his little body.