>>19847231. Get another bunny. They are not supposed to be kept alone.
2. Don't ever buy that standard market bunny food or "treats". They contain a ton of unhealthy shit for the bunny. Always have hay available in the pen and feed it fresh fruit, vegetables or some weeds from the field.
3. There's a lot of options for toys. Hay tunnels, small cat trees to hop onto the plateaus, unprinted cardboard boxes with entrances cut in, toilet paper rolls without the paper, etc. If you're very generous you can also offer them a digging box with sand/soil