You have 4 choices:

1. Enter 144.75 as a frequency and kill the guard using the fork or punches.
2. Use the fake death pill and when the guard walks in take the revival pill and kill him.
3. When the guard gives you food, throw it out the window 2 or 3 times and he goes to use the bathroom. Take this moment to call 144.75 and kill the guard on the toilet.
4. When the guard gives you food, throw it out the window 2 or 3 times and he goes to the bathroom. Wait for him to come back and you'll have a conversation. The guard then gives you cigar gas-spray thinking they are just cigars. Make him fall asleep and call 144.75 to get out.